Magnetic recording medium, tape cartridge, and data processing method

ABSTRACT

To provide a magnetic recording medium that has excellent traveling stability in spite of having a thin total thickness and a thin thickness of an underlayer, and is suitable for use in a recording/reproducing device for adjusting the width of the magnetic recording medium by adjusting a tension of the magnetic recording medium in a longitudinal direction thereof. 
     The present technology provides a tape-shaped magnetic recording medium including: a magnetic layer; an underlayer; a base layer; and a back layer, in which the underlayer has a thickness of 0.5 μm or more and 0.9 μm or less, the magnetic recording medium has an average thickness t T  of 5.6 μm or less, the magnetic recording medium includes a lubricant, the magnetic recording medium has pores, and the pores have an average diameter of 6 nm or more and 11 nm or less when the diameters of the pores are measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried, and the Young&#39;s modulus in a longitudinal direction is 7.90 GPa or less.

TECHNICAL FIELD

The present technology relates to a magnetic recording medium, a tapecartridge, and a data processing method.

BACKGROUND ART

For example, with development of IoT, big data, and artificialintelligence, the amount of data collected and stored has increasedsignificantly. A magnetic recording medium is often used as a medium forrecording a large amount of data.

Various techniques relating to a magnetic recording medium have beenproposed so far. For example, Patent Document 1 below discloses atechnique relating to a magnetic recording medium having a magneticlayer containing at least a binder and magnetic powder on at least onemain surface of a nonmagnetic support. In the magnetic recording medium,the thickness of the magnetic layer is 0.12 m or less, the root meansquare surface roughness (Rq) of the surface of the magnetic layerformation surface is 4.0 nm or less, and skewness (Sk) in the surfaceprofile of the magnetic layer formation surface is −1 or more and +1 orless.

Furthermore, in recent years, in a magnetic recording medium used as adata storage for a computer, a track width and a distance betweenadjacent tracks are very narrow in order to improve a data recordingdensity. When the track width and the distance between tracks are narrowin this way, a maximum allowable amount of change as the amount ofdimensional change of the tape itself due to an environmental factorsuch as changes in temperature and humidity is smaller.

Several techniques for reducing the amount of dimensional change havebeen proposed so far. For example, in a magnetic tape medium disclosedin Patent Document 2 below, when the Young's modulus of a nonmagneticsupport in a width direction thereof is represented by X and the Young'smodulus of a back layer in a width direction thereof is represented byY, X is 850 kg/mm² or more. Alternatively, in a case where X is lessthan 850 kg/mm², X×Y is 6×105 or more. When the Young's modulus of alayer including a magnetic layer in a width direction thereof isrepresented by Z, Y/Z is 6.0 or less.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2006-65953-   Patent Document 2: Japanese Patent Application Laid-Open No.    2005-332510

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A main object of the present technology is to provide a magneticrecording medium that has excellent traveling stability in spite ofhaving a thin total thickness and a thin thickness of an underlayer, andis suitable for use in a recording/reproducing device for adjusting thewidth of a magnetic recording medium by adjusting a tension of themagnetic recording medium in a longitudinal direction thereof.

Solutions to Problems

The present technology provides a tape-shaped magnetic recording mediumincluding: a magnetic layer; an underlayer; a base layer; and a backlayer, in which the underlayer has a thickness of 0.5 μm or more and 0.9μm or less, the magnetic recording medium has an average thickness t_(T)of 5.6 μm or less, the magnetic recording medium includes a lubricant,

the magnetic recording medium has pores, and the pores have an averagediameter of 6 nm or more and 11 nm or less when the diameters of thepores are measured in a state where the lubricant has been removed fromthe magnetic recording medium and the magnetic recording medium has beendried, and

the Young's modulus in a longitudinal direction is 7.90 GPa or less.

The magnetic recording medium can have a squareness ratio of 65% or morein a perpendicular direction thereof.

The magnetic layer side surface of the magnetic recording medium canhave arithmetic average roughness R_(a) of 2.5 nm or less.

The magnetic layer can have an average thickness t_(m) of 80 nm or less.

The base layer can include a polyester as a main component.

The ratio of the total thickness of the magnetic layer, the underlayer,and the back layer to the thickness of the base layer can be 0.3 orless.

The amount of dimensional change of the magnetic recording medium in awidth direction thereof between a state in which a tension of 0.5 N isapplied to the magnetic recording medium in a longitudinal directionthereof and a state in which a tension of 1.0 N is applied to themagnetic recording medium in the longitudinal direction can be 4.0 m ormore and 5.0 μm or less.

The magnetic layer includes magnetic powder, and the magnetic powder cancontain hexagonal ferrite, ε iron oxide, or Co iron oxide.

The hexagonal ferrite can contain at least one of Ba or Sr, and the εiron oxide can contain at least one of Al or Ga.

The magnetic recording medium can have a friction coefficient ratio(μ_(B)/μ_(A)) of 1.0 to 2.0, in which μ_(A) represents a coefficient ofdynamic friction between a magnetic layer side surface of the magneticrecording medium and a magnetic head in a state where a tension of 0.4 Nis applied to the magnetic recording medium in a longitudinal directionthereof, and μ_(B) represents a coefficient of dynamic friction betweenthe magnetic layer side surface of the magnetic recording medium and themagnetic head in a state where a tension of 1.2 N is applied to themagnetic recording medium in the longitudinal direction.

The magnetic recording medium can have a friction coefficient ratio(μ_(C(1000))/μ_(C(5))) of 1.0 to 2.0, in which μ_(C(5)) represents acoefficient of dynamic friction at fifth reciprocation in a case wherethe magnetic recording medium in a state where a tension of 0.6 N isapplied to the magnetic recording medium in a longitudinal directionthereof is reciprocatedly slid five times on a magnetic head, andμ_(C(1000)) represents a coefficient of dynamic friction at 1000threciprocation in a case where the magnetic recording medium isreciprocated 1000 times on the magnetic head.

The pores can have an average diameter of 6 nm or more and 10 nm orless.

The pores can have an average diameter of 7 nm or more and 9 nm or less.

The base layer can have an average thickness of 4.2 μm or less.

The back layer can have an average thickness of 0.5 μm or less.

The magnetic layer includes magnetic powder, and the magnetic powder canhave an average aspect ratio of 1.0 or more and 3.5 or less.

Furthermore, the present technology also provides a tape cartridgeincluding:

the tape-shaped magnetic recording medium according to the presenttechnology;

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in which

the information includes adjustment information for adjusting a tensionapplied to the magnetic recording medium in a longitudinal directionthereof.

The adjustment information can include dimensional information in thewidth direction at a plurality of positions in the longitudinaldirection of the magnetic recording medium.

Furthermore, the present technology also provides a data processingmethod, including:

a dimensional information acquiring step of acquiring dimensionalinformation in a width direction at a plurality of positions in alongitudinal direction of the tape-shaped magnetic recording mediumaccording to the present technology while the magnetic recording mediumis caused to travel with a tension applied in the longitudinaldirection; and

a data processing step of recording data on the magnetic recordingmedium and/or reproducing the data recorded on the magnetic recordingmedium while the magnetic recording medium is caused to travel with atension applied in the longitudinal direction, in which

in the data processing step, a tension applied to the magnetic recordingmedium in the longitudinal direction is adjusted on the basis of thedimensional information.

In the data processing step, a tension applied to the magnetic recordingmedium in a longitudinal direction thereof can be adjusted on the basisof the dimensional information and initial dimensional informationacquired in advance before the dimensional information acquiring step isperformed.

In the data processing step, a tension applied to the magnetic recordingmedium in a longitudinal direction thereof can be adjusted such that thedimensional information corresponds to the initial dimensionalinformation.

The data processing method may further include an information acquiringstep of acquiring at least one of environmental information around themagnetic recording medium or traveling condition information.

In the data processing step, a tension applied to the magnetic recordingmedium in a longitudinal direction thereof can be adjusted on the basisof the dimensional information and at least one of the environmentalinformation or the traveling condition information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of an example of a magneticrecording medium according to the present technology.

FIG. 2 is a diagram illustrating an example of data bands and servobands disposed in a magnetic recording medium.

FIG. 3 is a diagram illustrating an example of a servo pattern in aservo band.

FIG. 4 is a diagram illustrating an example of a servo pattern in aservo band.

FIG. 5 is a cross-sectional view illustrating a configuration of amagnetic particle.

FIG. 6 is a cross-sectional view illustrating a configuration of amagnetic particle in Modification.

FIG. 7 is a diagram for explaining a method for measuring a frictioncoefficient between a magnetic surface and a magnetic head.

FIG. 8 is a schematic diagram illustrating a configuration of arecording/reproducing device.

FIG. 9 is a schematic cross-sectional view of a magnetic recordingmedium in Modification.

FIG. 10 is an example of a TEM photograph of a magnetic layer.

FIG. 11A is a perspective view illustrating a configuration of ameasuring device.

FIG. 11B is a perspective view illustrating details of a measuringdevice.

FIG. 12 is an exploded perspective view illustrating an example of aconfiguration of a cartridge.

FIG. 13 is a block diagram illustrating an example of a configuration ofa cartridge memory.

FIG. 14 is a flowchart for explaining an example of arecording/reproducing method.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment for carrying out the presenttechnology will be described. Note that the embodiments described belowexemplify representative embodiments of the present technology, and thescope of the present technology is not limited only to the embodiments.

The present technology will be described in the following order.

1. Description of the present technology

2. Embodiment of the present technology (example of application typemagnetic recording medium)

(1) Configuration of magnetic recording medium

(2) Description of each layer

(3) Physical properties and structure

(4) Method for manufacturing magnetic recording medium

(5) Recording/reproducing device

(6) Cartridge

(7) Data processing method

(8) Effect

(9) Modification

3. Examples

1. DESCRIPTION OF THE PRESENT TECHNOLOGY

A magnetic recording medium is housed in, for example, a magneticrecording cartridge. In order to further increase the recording capacityper magnetic recording cartridge, it is considered to make a magneticrecording medium (for example, magnetic recording tape) housed in themagnetic recording cartridge thinner (to reduce the total thickness),and to increase the tape length per magnetic recording cartridge.Therefore, the total thickness of the magnetic recording medium isdesirably thin.

Furthermore, for recording or reproduction in the magnetic recordingmedium, a recording/reproducing device that can keep the width of thelong magnetic recording medium constant or substantially constant byadjusting a tension of the magnetic recording medium in a longitudinaldirection thereof may be used. The recording/reproducing device detects,for example, dimensions or a dimensional change of the magneticrecording medium in a width direction thereof, and adjusts the tensionin the longitudinal direction on the basis of a detection result. Forexample, in a case where a servo track width is wider than apredetermined width, the device increases the tension in thelongitudinal direction and keeps the servo track width constant, and ina case where the servo track width is narrower than the predeterminedwidth, the device decreases the tension in the longitudinal directionand keeps the servo track width constant. In this way, the width of themagnetic recording medium is kept constant. In order to adjust the widthof the magnetic recording medium by adjusting a tension of the magneticrecording medium in a longitudinal direction thereof, for example, theYoung's modulus of the magnetic recording medium is desirably low.

Therefore, the present inventors have studied a magnetic recordingmedium that is suitable for use in a recording/reproducing device thatadjusts the width of a magnetic recording medium by adjusting a tensionof the magnetic recording medium in a longitudinal direction thereof andhas a thin total thickness.

In order to reduce the total thickness of the magnetic recording medium,it is conceivable to reduce the thickness of the base layer constitutingthe majority of the total thickness of the magnetic recording medium.However, in general, in a magnetic recording medium, a base layer oftencontains a material that is softer and has a lower Young's modulus thana layer other than the base layer (for example, a polyester-based resinsuch as PET or PEN). For this reason, when the thickness of the baselayer is reduced, the constituent ratio of layers other than the baselayer increases, and the Young's modulus of the entire magneticrecording medium increases.

Therefore, it is conceivable to reduce the thickness of the underlayerin order to reduce the total thickness of the magnetic recording mediumwhile reducing the Young's modulus of the entire magnetic recordingmedium. However, in a case where the thickness of the underlayer isreduced, traveling stability may be adversely affected. For example, ina case where the underlayer includes a lubricant, an effect of improvingtraveling stability due to the lubricant is reduced by making theunderlayer thinner, and for example, a frictional force between themagnetic recording medium and a head can be increased.

The present inventors have found that a magnetic recording medium havinga specific configuration has excellent traveling stability in spite ofhaving a thin total thickness and a thin thickness of an underlayer, andis suitable for use in a recording/reproducing device for adjusting thewidth of the magnetic recording medium by adjusting a tension of themagnetic recording medium in a longitudinal direction thereof.

Specifically, the present inventors have studied various magneticrecording media each having a thin total thickness. As a result, thepresent inventors have found that a magnetic recording medium having aspecific configuration has excellent traveling stability in spite ofhaving a thin total thickness. That is, the magnetic recording mediumaccording to the present technology provides a tape-shaped magneticrecording medium including: a magnetic layer; an underlayer; a baselayer; and a back layer, in which the underlayer has a thickness of 0.5μm or more and 0.9 μm or less, the magnetic recording medium has anaverage thickness t_(T) of 5.6 μm or less, the magnetic recording mediumincludes a lubricant, the magnetic recording medium has pores, the poreshave an average diameter of 6 nm or more and 11 nm or less when thediameters of the pores are measured in a state where the lubricant hasbeen removed from the magnetic recording medium and the magneticrecording medium has been dried, and the Young's modulus in alongitudinal direction is 7.90 GPa or less.

The Young's modulus of the magnetic recording medium according to thepresent technology in a longitudinal direction thereof is 7.90 GPa orless, more preferably 7.85 or less, and still more preferably 7.80 GPaor less. The Young's modulus may be, for example, 3.00 GPa or more,preferably 4.00 Gpa or more, more preferably 5.00 Gpa or more, stillmore preferably 6.00 GPa or more, and further still more preferably 7.00GPa or more. The Young's modulus within the above numerical rangecontributes to achieving a magnetic recording medium that has a thintotal thickness and can adjust the dimensions in a width directionthereof by adjusting a tension applied to the magnetic recording mediumin a longitudinal direction thereof. For example, due to the Young'smodulus within the above numerical range, the magnetic recording mediumaccording to the present technology is suitable for use in arecording/reproducing device for adjusting the dimensions in the widthdirection by adjusting a tension in the longitudinal direction.

The magnetic recording medium according to the present technology haspores, and the pores have an average diameter of 6 nm or more and 11 nmor less when the diameters of the pores are measured in a state wherethe lubricant has been removed from the magnetic recording medium andthe magnetic recording medium has been dried. The average diameter ispreferably 10 nm or less, and more preferably 9 nm or less. The averagediameter is preferably 6.5 nm or more, more preferably 7 nm or more,still more preferably 7.5 nm or more, and particularly preferably 8 nmor more. The average diameter is more preferably 6 nm or more and 10 nmor less, still more preferably 6.5 nm or more and 10 nm or less, andfurther still more preferably 7 nm or more and 9 nm or less. The averagepore diameter within the numerical range described above can suppress anincrease in the coefficient of dynamic friction after repeated recordingor reproduction is performed. In a case where the average pore diameteris outside the numerical range described above, friction between themagnetic recording medium and the head gradually increases as themagnetic recording medium travels, and traveling stability maydeteriorate. It is considered that an appropriate amount of lubricantappears on the magnetic layer side surface due to the average diameterwithin the numerical range described above, and this contributes toimprovement in traveling stability of the magnetic recording mediumhaving a thin total thickness. The pores may be formed, for example, ona surface of the magnetic recording medium, more particularly on asurface of the magnetic layer side. The pores may be present, forexample, in the magnetic layer. The pores present in the magnetic layermay be formed only in the magnetic layer, or the pores formed in themagnetic layer may extend to another layer, for example, to theunderlayer.

The thickness of the underlayer of the magnetic recording mediumaccording to the present technology is 0.5 μm or more and 0.9 μm orless, and preferably 0.6 μm or more and 0.8 μm or less. The thickness ofthe underlayer within the above numerical range contributes to bothlowering the Young's modulus while reducing the total thickness andstably supplying the lubricant to the magnetic layer side surface. Thatis, in the magnetic recording medium, the thickness of the underlayerwithin the above numerical range improves the suitability for use in theabove recording/reproducing device and traveling stability.

The average thickness t_(T) of the magnetic recording medium accordingto the present technology can be 5.6 μm or less, more preferably 5.3 μmor less, and still more preferably 5.2 μm or less, 5.0 μm or less, or4.6 μm or less. Since the magnetic recording medium according to thepresent technology has such a thin total thickness, for example, a tapelength wound around one magnetic recording cartridge can be made longer,thereby increasing the recording capacity per magnetic recordingcartridge.

The width of the magnetic recording medium according to the presenttechnology can be, for example, 5 mm to 30 mm, particularly 7 mm to 25mm, more particularly 10 mm to 20 mm, and still more particularly 11 mmto 19 mm. The length of the tape-shaped magnetic recording mediumaccording to the present technology can be, for example, 500 m to 1500m. For example, the tape width according to the LTO8 standard is 12.65mm and the length according thereto is 960 m.

The magnetic recording medium according to the present technology has atape shape, and can be, for example, a long magnetic recording tape. Thetape-shaped magnetic recording medium according to the presenttechnology may be housed in a magnetic recording cartridge, for example.More specifically, the magnetic recording medium may be housed in thecartridge while being wound around a reel in the magnetic recordingcartridge.

The magnetic recording medium according to the present technologyincludes a magnetic layer, an underlayer, a base layer, and a backlayer. These four layers may be laminated in this order. In addition tothese layers, the magnetic recording medium according to the presenttechnology may include another layer. The other layer may beappropriately selected according to the type of the magnetic recordingmedium. The magnetic recording medium according to the presenttechnology can be, for example, an application type magnetic recordingmedium. The application type magnetic recording medium will be describedin more detail in the following column 2.

According to a preferred embodiment of the present technology, in themagnetic recording medium, a squareness ratio in a perpendiculardirection can be 65% or more, a surface roughness R_(a) of the magneticlayer side surface of the magnetic recording medium can be 2.5 nm orless, and an average thickness t_(m) of the magnetic layer can be 80 nmor less. As a result, recording/reproducing characteristics in the thinmagnetic recording medium are improved.

The tape-shaped magnetic recording medium according to the presenttechnology includes: a magnetic layer; an underlayer; a base layer; anda back layer, in which the underlayer has a thickness of 0.5 μm or moreand 0.9 μm or less, the magnetic recording medium has an averagethickness t_(T) of 5.6 μm or less, the magnetic recording mediumincludes a lubricant, the magnetic recording medium has pores, the poreshave an average diameter (pore diameter when the pore volume is maximumat the time of gas desorption to the pores) of 6 nm or more and 11 nm orless when the diameters of the pores are measured in a state where thelubricant has been removed from the magnetic recording medium and themagnetic recording medium has been dried, the Young's modulus in thelongitudinal direction is 7.90 GPa or less, and the ratio of the totalthickness of the magnetic layer, the underlayer, and the back layer tothe thickness of the base layer may be 0.38 or less.

The magnetic recording medium has excellent traveling stability in spiteof having a thin total thickness and a thin thickness of an underlayer,and is suitable for use in a recording/reproducing device for adjustingthe width of the magnetic recording medium by adjusting the tension ofthe magnetic recording medium in a longitudinal direction thereof.

Moreover, it has been found that a ratio between the total thickness ofrelatively hard coating layers (magnetic layer, underlayer, and backlayer) and the thickness of the relatively soft base layer is importantfor suitability for use in a recording/reproducing device for adjustingthe width of the magnetic recording medium by adjusting a tension of themagnetic recording medium in a longitudinal direction thereof. Byadjusting the ratio within the above numerical range, it is easier toachieve both traveling stability and ease of tension adjustment.

The tape-shaped magnetic recording medium according to the presenttechnology includes: a magnetic layer; an underlayer; a base layer; anda back layer, in which the underlayer has a thickness of 0.5 μm or moreand 0.9 μm or less, the magnetic recording medium has an averagethickness t_(T) of 5.6 μm or less, the magnetic recording mediumincludes a lubricant, the magnetic recording medium has pores, the poreshave an average diameter (pore diameter when the pore volume is maximumat the time of gas desorption to the pores) of 6 nm or more and 11 nm orless when the diameters of the pores are measured in a state where thelubricant has been removed from the magnetic recording medium and themagnetic recording medium has been dried, the Young's modulus in alongitudinal direction is 7.90 GPa or less, and a friction coefficientratio (μ_(B)/μ_(A)) may be 1.0 to 2.0, in which μ_(A) represents acoefficient of dynamic friction between a magnetic layer side surface ofthe magnetic recording medium and a magnetic head in a state where atension of 0.4 N is applied to the magnetic recording medium in alongitudinal direction thereof, and μ_(B) represents a coefficient ofdynamic friction between the magnetic layer side surface of the magneticrecording medium and the magnetic head in a state where a tension of 1.2N is applied to the magnetic recording medium in the longitudinaldirection.

The magnetic recording medium has excellent traveling stability in spiteof having a thin total thickness and a thin thickness of an underlayer,and is suitable for use in a recording/reproducing device for adjustingthe width of the magnetic recording medium by adjusting the tension ofthe magnetic recording medium in a longitudinal direction thereof.Moreover, due to the friction coefficient ratio (μ_(B)/μ_(A)) within theabove numerical range, the magnetic recording medium has a frictioncoefficient with the head within a certain range even if a tension thataffects a contact state with the head is changed, and has excellenttraveling stability.

The tape-shaped magnetic recording medium according to the presenttechnology includes: a magnetic layer; an underlayer; a base layer; anda back layer, in which the underlayer has a thickness of 0.5 μm or moreand 0.9 μm or less, the magnetic recording medium has an averagethickness t_(T) of 5.6 μm or less, the magnetic recording mediumincludes a lubricant, the magnetic recording medium has pores, the poreshave an average diameter (pore diameter when the pore volume is maximumat the time of gas desorption to the pores) of 6 nm or more and 11 nm orless when the diameters of the pores are measured in a state where thelubricant has been removed from the magnetic recording medium and themagnetic recording medium has been dried, the Young's modulus in alongitudinal direction is 7.90 GPa or less, a friction coefficient ratio(μ_(B)/μ_(A)) is 1.0 to 2.0, in which μ_(A) represents a coefficient ofdynamic friction between a magnetic layer side surface of the magneticrecording medium and a magnetic head in a state where a tension of 0.4 Nis applied to the magnetic recording medium in a longitudinal directionthereof, and μ_(B) represents a coefficient of dynamic friction betweenthe magnetic layer side surface of the magnetic recording medium and themagnetic head in a state where a tension of 1.2 N is applied to themagnetic recording medium in the longitudinal direction, and a frictioncoefficient ratio (μ_(C(1000))/μ_(C(5))) may be 1.0 to 2.0, in whichμ_(C(5)) represents a coefficient of dynamic friction at the fifthreciprocation in a case where the magnetic recording medium in a statewhere a tension of 0.6 N is applied to the magnetic recording medium ina longitudinal direction thereof is reciprocatedly slid five times on amagnetic head, and μ_(C(1000)) represents a coefficient of dynamicfriction at the 1000th reciprocation in a case where the magneticrecording medium is reciprocated 1000 times on the magnetic head.

The magnetic recording medium has excellent traveling stability in spiteof having a thin total thickness and a thin thickness of an underlayer,and is suitable for use in a recording/reproducing device for adjustingthe width of the magnetic recording medium by adjusting the tension ofthe magnetic recording medium in a longitudinal direction thereof.Moreover, due to the friction coefficient ratios (μ_(B)/μ_(A)) and(μ_(C(1000))/μ_(C(5))) within the above numerical ranges, the magneticrecording medium has a friction coefficient with the head within acertain range even if travel is repeated and a tension that affects acontact state with the head is changed, and can exhibit stable travelingperformance all the time.

2. EMBODIMENT OF THE PRESENT TECHNOLOGY (EXAMPLE OF APPLICATION TYPEMAGNETIC RECORDING MEDIUM) (1) Configuration of Magnetic RecordingMedium

First, a configuration of a magnetic recording medium 10 according to afirst embodiment will be described with reference to FIG. 1 . Themagnetic recording medium 10 is, for example, a magnetic recordingmedium that has been perpendicularly orientated, and as illustrated inFIG. 1 , includes a long base layer (also referred to as a substrate)11, an underlayer (nonmagnetic layer) 12 disposed on one main surface ofthe base layer 11, a magnetic layer (also referred to as a recordinglayer) 13 disposed on the underlayer 12, and a back layer 14 disposed onthe other main surface of the base layer 11. Here, out of both mainsurfaces of the magnetic recording medium 10, the surface on which themagnetic layer 13 is disposed is also referred to as a magnetic surfaceor a magnetic layer side surface, and the surface opposite to themagnetic surface (surface on which the back layer 14 is disposed) isalso referred to as a back surface.

The magnetic recording medium 10 has a tape shape and travels in alongitudinal direction thereof during recording and reproduction.Furthermore, the magnetic recording medium 10 may be able to record asignal at the shortest recording wavelength of preferably 100 nm orless, more preferably 75 nm or less, still more preferably 60 nm orless, particularly preferably 50 nm or less, and can be used, forexample, for a recording/reproducing device having the shortestrecording wavelength within the range described above. Thisrecording/reproducing device may include a ring type head as a recordinghead. The recording track width can be, for example, 2 m or less.

(2) Description of Each Layer

(Base Layer)

The base layer 11 can function as a support for the magnetic recordingmedium 10, and is, for example, a long nonmagnetic substrate havingflexibility, and in particular, can be a nonmagnetic film. The thicknessof the base layer 11 is, for example, 8 μm or less, preferably 7 μm orless, more preferably 6 μm or less, still more preferably 5 μm or less,and particularly preferably 4.2 μm or less. The thickness of the baselayer 11 can be, for example, 2 μm or more, preferably 2.2 μm or more,more preferably 2.5 μm or more, and still more preferably 2.6 μm ormore.

The average thickness of the base layer 11 can be determined as follows.First, the magnetic recording medium 10 having a width of ½ inches isprepared and cut into a length of 250 mm to manufacture a sample.Subsequently, layers of the sample other than the base layer 11 (thatis, the underlayer 12, the magnetic layer 13, and the back layer 14) areremoved with a solvent such as methyl ethyl ketone (MEK) or dilutehydrochloric acid. Next, the thickness of the sample (base layer 11) ismeasured at five or more points using a laser hologage (LGH-110C)manufactured by Mitutoyo Corporation as a measuring device, and themeasured values are simply averaged (arithmetically averaged) tocalculate the average thickness of the base layer 11. Note that themeasurement points are randomly selected from the sample. Here, a valuecalculated by the measuring device is described to the first decimalplace by rounding off the second decimal place.

In one embodiment of the present technology, the base layer 11 caninclude, for example, a polyester as a main component. The polyestermakes it easy to adjust the Young's modulus of the magnetic recordingmedium 10 in a longitudinal direction thereof within the above numericalrange. The polyester may be, for example, one of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polybutyleneterephthalate (PBT), polybutylene naphthalate (PBN),polycyclohexylenedimethylene terephthalate (PCT),polyethylene-p-oxybenzoate (PEB), polyethylene bisphenoxycarboxylate,and polyether ether ketone (PEEK), or a mixture of two or more thereof.Here, the “main component” means a component having the highest contentratio among the components constituting the base layer. For example,inclusion of a polyester in the base layer 11 as a main component maymean that the content ratio of the polyester in the base layer 11 is,for example, 50% by mass or more, 60% by mass or more, 70% by mass ormore, 80% by mass or more, 90% by mass or more, 95% by mass or more, or98% by mass or more with respect to the mass of the base layer 11, ormay mean that the base layer 11 includes only a polyester.

In this embodiment, the base layer 11 may include a resin other than thepolyester, described below, in addition to a polyester.

According to a preferred embodiment of the present technology, the baselayer 11 may include PET or PEN.

In another embodiment of the present technology, the base layer 11 mayinclude a resin other than the polyester-based resin. The resin formingthe base layer 11 can contain, for example, at least one of apolyolefin-based resin, a cellulose derivative, a vinyl-based resin, oranother polymer resin. In a case where the base layer 11 includes two ormore of these resins, the two or more materials may be mixed,copolymerized, or laminated.

The polyolefin-based resin includes, for example, at least one ofpolyethylene (PE) or polypropylene (PP). The cellulose derivativeincludes, for example, at least one of cellulose diacetate, cellulosetriacetate, cellulose acetate butyrate (CAB), or cellulose acetatepropionate (CAP). The vinyl-based resin includes, for example, at leastone of polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC).

The other polymer resin includes, for example, at least one of polyetherether ketone (PEEK), polyamide or nylon (PA), aromatic polyamide oraramid (aromatic PA), polyimide (PI), aromatic polyimide (aromatic PI),polyamide imide (PAI), aromatic polyamide imide (aromatic PAI),polybenzoxazole (PBO) such as ZYLON (registered trademark), polyether,polyether ketone (PEK), polyether ester, polyether sulfone (PES),polyether imide (PEI), polysulfone (PSF), polyphenylene sulfide (PPS),polycarbonate (PC), polyarylate (PAR), or polyurethane (PU). Accordingto a preferred embodiment of the present technology, the base layer 11may include PEEK.

(Magnetic Layer)

The magnetic layer 13 can be, for example, a perpendicular recordinglayer. The magnetic layer 13 can include magnetic powder and alubricant. The magnetic layer 13 may include, for example, a binder inaddition to the magnetic powder and the lubricant, and may furtherinclude a binder and conductive particles, in particular. The magneticlayer 13 may further include an additive such as an abrasive or a rustpreventive as necessary.

The magnetic layer 13 has pores. That is, the magnetic layer 13 has asurface having a large number of pores. Preferably, in the magneticlayer 13, pores are formed in an area in contact with a magnetic head inrecording and/or reproduction of the magnetic recording medium 10, andparticularly preferably, pores may be formed over the entire area.

The pores may be opened perpendicularly to the surface of the magneticlayer 13. The pores can be formed, for example, by pressing a largenumber of protrusions formed on the back layer side surface of themagnetic recording medium 10. In this case, the pores can correspond tothe protrusions.

Note that in FIG. 1 , the pores are indicated by reference numeral 13A,but FIG. 1 is a schematic diagram for better understanding of thepresent technology. The shapes of the pores 13A illustrated in FIG. 1 donot necessarily indicate the actual shapes.

The average thickness t_(m) of the magnetic layer 13 can satisfypreferably 35 nm≤t_(m)≤120 nm, more preferably 35 nm≤t_(m)≤100 nm,particularly preferably 35 nm≤t_(m)≤90 nm. The average thickness t_(m)of the magnetic layer 13 within the above numerical range contributes toimprovement in electromagnetic conversion characteristics.

The average thickness t_(m) of the magnetic layer is particularlypreferably 80 nm or less. The average thickness t_(m) of the magneticlayer within this numerical range contributes to improvement in therecording/reproducing characteristics of the magnetic recording medium10.

The average thickness t_(m) of the magnetic layer 13 is determined asfollows, for example.

The magnetic recording medium 10 is processed to be thinned by a focusedion beam (FIB) method and the like. In a case where the FIB method isused, as a pretreatment for observing a TEM image of a cross sectiondescribed later, a carbon film and a tungsten thin film are formed asprotective films. The carbon film is formed on the magnetic layer sidesurface and the back layer side surface of the magnetic recording medium10 by a vapor deposition method, and the tungsten thin film is furtherformed on the magnetic layer side surface by a vapor deposition methodor a sputtering method. The thinning is performed in a length direction(longitudinal direction) of the magnetic recording medium 10. That is,by the thinning, a cross section parallel to both the longitudinaldirection and the thickness direction of the magnetic recording medium10 is formed.

The cross section of the obtained thinned sample is observed with atransmission electron microscope (TEM) under the following conditions toobtain a TEM image. Note that the magnification and the accelerationvoltage may be appropriately adjusted according to the type of device.

Device: TEM (H9000NAR manufactured by Hitachi, Ltd.)

Acceleration voltage: 300 kV

Magnification: 100,000 times

Next, using the obtained TEM image, the thickness of the magnetic layer13 is measured at 10 or more points in the longitudinal direction of themagnetic recording medium 10. An average value obtained by simplyaveraging (arithmetically averaging) the obtained measurement values isdefined as the average thickness t_(m) [nm] of the magnetic layer 13.Note that the points where the measurement is performed are randomlyselected from a test piece.

The magnetic layer 13 is preferably a perpendicularly oriented magneticlayer. Here, the perpendicular orientation means that a squareness ratioS1 measured in the longitudinal direction (traveling direction) of themagnetic recording medium 10 is 35% or less. A method for measuring thesquareness ratio S1 will be separately described below.

Note that the magnetic layer 13 may be a magnetic layer that is in-planeoriented (longitudinally oriented). That is, the magnetic recordingmedium 10 may be a horizontal recording type magnetic recording medium.However, the perpendicular orientation is more preferable in terms ofincreasing the recording density.

(Servo Pattern)

A servo pattern is recorded on the magnetic layer 13. For example, asillustrated in FIG. 2A, the magnetic layer may have a plurality of servobands SB and a plurality of data bands DB. The plurality of servo bandsSB is disposed at regular intervals in a width direction of the magneticrecording medium 10. A data band DB is disposed between adjacent servobands SB. In each of the servo bands SB, a servo signal for performingtracking control of a magnetic head may be written in advance. User datacan be recorded in the data band DB.

The magnetic layer 13 can have, for example, at least one data band andat least two servo bands. The number of data bands can be, for example 2to 10, particularly 3 to 6, and more particularly 4 or 5. The number ofservo bands can be, for example, 3 to 11, particularly 4 to 7, and moreparticularly 5 or 6. These servo bands and data bands may be disposed,for example, so as to extend in the longitudinal direction of atape-shaped magnetic recording medium (particularly, a long magneticrecording tape), in particular, so as to be in substantially parallel toeach other. Examples of such a magnetic recording medium having a databand and a servo band include a magnetic recording tape according to thelinear tape-open (LTO) standard. That is, the magnetic recording mediumaccording to the present technology may be a magnetic recording tapeaccording to the LTO standard. For example, the magnetic recordingmedium according to the present technology may be a magnetic recordingtape according to LTO8 or a later standard.

A ratio RS(=(SSB/S)×100) of a total area SSB of the servo bands SB withrespect to an area S of the entire surface of the magnetic layer 13 ispreferably 4.0% or less, more preferably 3.0% or less, and still morepreferably 2.0% or less from a viewpoint of securing a high recordingcapacity.

Note that a servo bandwidth WSB of each of the servo bands SB ispreferably 95 m or less, more preferably 60 μm or less, and still morepreferably 30 μm or less from a viewpoint of securing a high recordingcapacity. The servo bandwidth WSB is preferably 10 μm or more from aviewpoint of manufacturing a recording head.

The magnetic layer 13 can have, for example, five or more servo bands.The ratio RS of the total area SSB of the servo bands SB with respect tothe area S of the surface of the magnetic layer 13 can be preferably0.8% or more in order to secure five or more servo tracks.

The ratio RS of the total area SSB of the servo bands SB with respect tothe area S of the entire surface of the magnetic layer 13 is determinedas follows. For example, the magnetic recording medium 10 is developedusing a ferricolloid developer (Sigmarker Q manufactured by SigmaHi-Chemical Inc.), then the developed magnetic recording medium 10 isobserved with an optical microscope, and the servo bandwidth WSB and thenumber of servo bands SB are measured. Next, the ratio R_(S) isdetermined from the following formula.Ratio RS[%]=(((servo bandwidth WSB)×(number of servo bands))/(width ofmagnetic recording medium 10))×100

As illustrated in FIG. 2B, the magnetic layer 13 can form a plurality ofdata tracks Tk in a data band DB. In this case, a data track width WTkis preferably 2.0 m or less, more preferably 1.5 m or less, and stillmore preferably 1.0 m or less from a viewpoint of securing a highrecording capacity. The data track width WTk is preferably 0.02 m ormore from a viewpoint of a magnetic particle size. The data track widthWTk is determined as follows. For example, a data recording pattern of adata band portion of the magnetic layer 13 on the entire surface ofwhich data is recorded is observed using a magnetic force microscope(MFM) to obtain an MFM image. As the MFM, Dimension 3100 manufactured byDigital Instruments and analysis software thereof are used. Ameasurement area of the MFM image is set to 10 μm×10 μm, and themeasurement area of 10 μm×10 μm is divided into 512×512 (=262,144)measurement points. Measurement is performed with the MFM on three 10μm×10 μm measurement areas at different locations, that is, three MFMimages are obtained. From the three obtained MFM images, using theanalysis software attached to Dimension 3100, the track width ismeasured at 10 locations and an average value (simple average) is taken.The average value is the data track width WTk. Note that the MFMmeasurement conditions are: sweep speed: 1 Hz, chip used: MFMR-20, liftheight: 20 nm, and correction: Flatten order 3.

The magnetic layer 13 can record data such that a minimum value of thedistance L between magnetization inversions is preferably 48 nm or less,more preferably 44 nm or less, and still more preferably 40 nm or lessfrom a viewpoint of securing a high recording capacity. The minimumvalue of the distance L between magnetization inversions is considereddepending on a magnetic particle size. The minimum value of the distanceL between magnetization inversions is determined as follows. Forexample, a data recording pattern of a data band portion of the magneticlayer 13 on the entire surface of which data is recorded is observedusing a magnetic force microscope (MFM) to obtain an MFM image. As theMFM, Dimension 3100 manufactured by Digital Instruments and analysissoftware thereof are used. The measurement area of the MFM image is setto 2 μm×2 μm, and the measurement area of 2 μm×2 μm is divided into512×512 (=262,144) measurement points. Measurement is performed with theMFM on three 2 μm×2 μm measurement areas at different locations, thatis, three MFM images are obtained. 50 distances between bits aremeasured from a two-dimensional uneven chart of a recording pattern ofthe obtained MFM image. The distance between bits is measured using theanalysis software attached to Dimension 3100. A value that isapproximately the greatest common divisor of the measured 50 distancesbetween bits is defined as the minimum value of the distance L betweenmagnetization inversions. Note that the measurement conditions are:sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, andcorrection: Flatten order 3.

More specific examples of the servo pattern recorded on the magneticlayer 13 of the magnetic recording medium of the present technology willbe described below with reference to FIGS. 3 and 4 . FIG. 3 is aschematic diagram of a data band and a servo band formed in the magneticlayer 13 of the magnetic recording medium 10. FIG. 4 is a diagramillustrating a servo pattern included in each servo band.

As illustrated in FIG. 3 , the magnetic layer 13 has four data bands d0to d3. The magnetic layer 13 has five servo bands S0 to S4 in total suchthat each data band is sandwiched between two servo bands.

As illustrated in FIG. 4 , each servo band repeatedly has a frame unit(one servo frame) including five linear servo patterns inclined at apredetermined angle φ (for example, servo patterns A1 to A5), fivelinear servo patterns inclined at the same angle in the oppositedirection to this signal (for example, servo patterns B1 to B5), fourlinear servo patterns inclined at a predetermined angle φ (for example,servo patterns C1 to C4), and four linear servo patterns inclined at thesame angle in the opposite direction to this signal (for example, servopatterns D1 to D4). The predetermined angle φ can be, for example, 5° to25°, and particularly 11° to 25°.

A servo bandwidth L1 (see FIG. 3 ) of each of the servo bands S0 to S4may be, for example, 100 μm or less, particularly 60 μm or less, moreparticularly 50 μm or less, and further 40 μm or less. The servobandwidth L1 may be, for example, 15 μm or more, and particularly 25 μmor more.

(Magnetic Powder)

Examples of a magnetic particle forming the magnetic powder included inthe magnetic layer 13 include hexagonal ferrite, epsilon-type iron oxide(ε iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite,chromium dioxide, cobalt-coated iron oxide, and metal, but are notlimited thereto. The magnetic powder may be one of these or acombination of two or more thereof. Preferably, the magnetic powder cancontain hexagonal ferrite, ε iron oxide, or Co-containing spinelferrite. Particularly preferably, the magnetic powder is hexagonalferrite. The hexagonal ferrite can particularly preferably contain atleast one of Ba or Sr. The ε iron oxide can particularly preferablycontain at least one of Al or Ga. These magnetic particles may beappropriately selected by those skilled in the art on the basis offactors such as a method for manufacturing the magnetic layer 13, thestandard of the tape, and the function of the tape.

The shape of the magnetic particle depends on the crystal structure ofthe magnetic particle. For example, the barium ferrite (BaFe) and thestrontium ferrite can each have a hexagonal plate shape. The ε ironoxide can be spherical. The cobalt ferrite can be cubic. The metal canbe spindle-shaped. In a step of manufacturing the magnetic recordingmedium 10, these magnetic particles are oriented.

The average particle size of the magnetic powder can be preferably 50 nmor less, more preferably 40 nm or less, and still more preferably 30 nmor less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less.The average particle size can be, for example, 10 nm or more, andpreferably 12 nm or more.

The aspect ratio of the magnetic powder can be preferably 1.0 or moreand 3.5 or less, more preferably 1.0 or more and 3.1 or less, still morepreferably 1.0 or more and 2.8 or less, and particularly preferably 1.1or more and 2.5 or less.

(Embodiment in which Magnetic Powder Contains Hexagonal Ferrite)

According to a preferred embodiment of the present technology, themagnetic powder can contain hexagonal ferrite, and more particularly cancontain powder of nanoparticles containing hexagonal ferrite(hereinafter referred to as “hexagonal ferrite particles”). Thehexagonal ferrite particle has, for example, a hexagonal plate shape ora substantially hexagonal plate shape. The hexagonal ferrite canpreferably contain at least one of Ba, Sr, Pb, or Ca, more preferably atleast one of Ba or Sr. Specifically, the hexagonal ferrite may be, forexample, barium ferrite or strontium ferrite. The barium ferrite mayfurther contain at least one of Sr, Pb, or Ca in addition to Ba. Thestrontium ferrite may further contain at least one of Ba, Pb, or Ca inaddition to Sr.

More specifically, the hexagonal ferrite can have an average compositionrepresented by a general formula MFe₁₂O₁₉. Here, M represents, forexample, at least one metal of Ba, Sr, Pb, and Ca, preferably at leastone metal of Ba and Sr. M may represent a combination of Ba and one ormore metals selected from the group including Sr, Pb, and Ca.Furthermore, M may represent a combination of Sr and one or more metalsselected from the group including Ba, Pb, and Ca. In the above generalformula, some of Fe atoms may be replaced with another metal element.

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, the average particle size of the magnetic powder can bepreferably 50 nm or less, more preferably 40 nm or less, and still morepreferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less,or 20 nm or less. The average particle size can be, for example, 10 nmor more, preferably 12 nm or more, and more preferably 15 nm or more.For example, the average particle size of the magnetic powder can be 10nm or more and 50 nm or less, 10 nm or more and 40 nm or less, 12 nm ormore and 30 nm or less, 12 nm or more and 25 nm or less, or 15 nm ormore and 22 nm or less. In a case where the average particle size of themagnetic powder is the upper limit value described above or less (forexample, 50 nm or less, particularly 30 nm or less), in the magneticrecording medium 10 having a high recording density, goodelectromagnetic conversion characteristics (for example, C/N) can beobtained. In a case where the average particle size of the magneticpowder is the lower limit value described above or more (for example, 10nm or more, preferably 12 nm or more), the dispersibility of themagnetic powder is further improved, and better electromagneticconversion characteristics (for example, C/N) can be obtained.

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, the average aspect ratio of the magnetic powder can bepreferably 1 or more and 3.2 or less, more preferably 1 or more and 2.5or less, still more preferably 1 or more and 2.1 or less, and furtherstill more preferably 1 or more and 1.8 or less. When the average aspectratio of the magnetic powder is within the above numerical range,aggregation of the magnetic powder can be suppressed, and moreover,resistance applied to the magnetic powder can be suppressed when themagnetic powder is perpendicularly oriented in a step of forming themagnetic layer 13. This can improve the perpendicular orientation of themagnetic powder.

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, the average particle size and average aspect ratio of themagnetic powder are determined as follows.

First, the magnetic recording medium 10 to be measured is processed tobe thinned by a focused ion beam (FIB) method and the like. In a casewhere the FIB method is used, as a pretreatment for observing a TEMimage of a cross section described later, a carbon film and a tungstenthin film are formed as protective films. The carbon film is formed onthe magnetic layer side surface and the back layer side surface of themagnetic recording medium 10 by a vapor deposition method, and thetungsten thin film is further formed on the magnetic layer side surfaceby a vapor deposition method or a sputtering method. The thinning isperformed in a length direction (longitudinal direction) of the magneticrecording medium 10. That is, by the thinning, a cross section parallelto both the longitudinal direction and the thickness direction of themagnetic recording medium 10 is formed.

Cross-sectional observation is performed for the cross section of theobtained thin sample such that the entire magnetic layer 13 is includedwith respect to the thickness direction of the magnetic layer 13 using atransmission electron microscope (H-9500 manufactured by HitachiHigh-Technologies) with an acceleration voltage of 200 kV and an overallmagnification of 500,000 times, and a TEM photograph is imaged.

Next, from the imaged TEM photograph, 50 particles which have sidesurfaces directed to an observation surface and the thicknesses of whichcan be clearly confirmed are selected. For example, FIG. 10 illustratesan example of the TEM photograph. In FIG. 10 , for example, particlesindicated by a and d are selected because their thicknesses can beclearly confirmed. A maximum plate thickness DA of each of the 50selected particles is measured. The maximum plate thicknesses DA thusdetermined are simply averaged (arithmetically averaged) to determine anaverage maximum plate thickness DA_(ave).

Subsequently, the plate diameter DB of each particle of the magneticpowder is measured. In order to measure the particle plate diameter DB,50 particles the plate diameters of which can be clearly confirmed areselected from the imaged TEM photograph. For example, in FIG. 10 , forexample, particles indicated by b and c are selected because their platediameters can be clearly confirmed. The plate diameter DB of each of the50 selected particles is measured. The plate diameters DB thusdetermined are simply averaged (arithmetically averaged) to determine anaverage plate diameter DB_(ave). The average plate diameter DB_(ave) isthe average particle size.

Then, an average aspect ratio (DB_(ave)/DA_(ave)) of the particles isdetermined from the average maximum plate thickness DA_(ave) and theaverage plate diameter DB_(ave).

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, the average particle volume of the magnetic powder ispreferably 5900 nm³ or less, more preferably 500 nm³ or more and 3400nm³ or less, and still more preferably 1000 nm³ or more and 2500 nm³ orless.

In a case where the average particle volume of the magnetic powder isthe upper limit value described above or less (for example, 5900 nm³ orless), good electromagnetic conversion characteristics (for example,C/N) can be obtained in the magnetic recording medium 10 having a highrecording density. In a case where the average particle volume of themagnetic powder is the lower limit value described above or more (forexample, 500 nm³ or more), the dispersibility of the magnetic powder isfurther improved, and better electromagnetic conversion characteristics(for example, C/N) can be obtained.

The average particle volume of the magnetic powder is determined asfollows. First, the average maximum plate thickness DA_(ave) and theaverage plate diameter DB_(ave) are determined as described regardingthe above-described method for calculating the average particle size ofthe magnetic powder. Next, an average volume V of the magnetic powder isdetermined by the following formula.

$V = {\frac{3\sqrt{3}}{8} \times {DA}_{ave} \times {DB}_{ave} \times {DB}_{ave}}$

According to a particularly preferred embodiment of the presenttechnology, the magnetic powder can be barium ferrite magnetic powder orstrontium ferrite magnetic powder, and more preferably barium ferritemagnetic powder. The barium ferrite magnetic powder includes iron oxidemagnetic particles having barium ferrite as a main phase (hereinafterreferred to as “barium ferrite particles”). The barium ferrite magneticpowder has high data recording reliability, for example, does notdecrease a coercive force even in a high-temperature and high-humidityenvironment. The barium ferrite magnetic powder is preferable as themagnetic powder from such a viewpoint.

The average particle size of the barium ferrite magnetic powder is 50 nmor less, more preferably 10 nm or more and 40 nm or less, and still morepreferably 12 nm or more and 25 nm or less.

In a case where the magnetic layer 13 contains barium ferrite magneticpowder as the magnetic powder, the average thickness t_(m) [nm] of themagnetic layer 13 preferably satisfies 35 nm≤t_(m)≤100 nm, and isparticularly preferably 80 nm or less.

Furthermore, the coercive force He measured in a thickness direction(perpendicular direction) of the magnetic recording medium 10 ispreferably 160 kA/m or more and 280 kA/m or less, more preferably 165kA/m or more and 275 kA/m or less, and still more preferably 170 kA/m ormore and 270 kA/m or less.

(Embodiment in which Magnetic Powder Contains ε Iron Oxide)

According to another preferred embodiment of the present technology, themagnetic powder can preferably contain powder of nanoparticlescontaining ε iron oxide (hereinafter referred to as “ε iron oxideparticles”). Even if the ε iron oxide particles are fine particles, ahigh coercive force can be obtained. ε iron oxide contained in the εiron oxide particles is preferably crystal-oriented preferentially in athickness direction (perpendicular direction) of the magnetic recordingmedium 10.

The ε iron oxide particle has a spherical shape or a substantiallyspherical shape, or has a cubic shape or a substantially cubic shape.Since the ε iron oxide particle has the shape as described above, in acase where the E iron oxide particles are used as magnetic particles, acontact area between the particles in a thickness direction of themedium can be reduced, and aggregation of the particles can besuppressed as compared to a case where hexagonal plate-shaped bariumferrite particles are used as the magnetic particles. Therefore,dispersibility of the magnetic powder can be enhanced, and a bettersignal-to-noise ratio (SNR) can be obtained.

The ε iron oxide particle has a core-shell type structure. Specifically,the ε iron oxide particle has a core portion 21 and a two-layered shellportion 22 disposed around the core portion 21 as illustrated in FIG. 5. The two-layered shell portion 22 includes a first shell portion 22 adisposed on the core portion 21 and a second shell portion 22 b disposedon the first shell portion 22 a.

The core portion 21 contains ε iron oxide. ε iron oxide contained in thecore portion 21 preferably contains an ε-Fe₂O₃ crystal as a main phase,and more preferably contains ε—Fe₂O₃ as a single phase.

The first shell portion 22 a covers at least a part of the periphery ofthe core portion 21. Specifically, the first shell portion 22 a maypartially cover the periphery of the core portion 21 or may cover theentire periphery of the core portion 21. The first shell portion 22 apreferably covers the entire surface of the core portion 21 from aviewpoint of making exchange coupling between the core portion 21 andthe first shell portion 22 a sufficient and improving magneticcharacteristics.

The first shell portion 22 a is a so-called soft magnetic layer, and caninclude, for example, a soft magnetic material such as α-Fe, a Ni—Fealloy, or a Fe—Si—Al alloy. α-Fe may be obtained by reducing ε ironoxide contained in the core portion 21.

The second shell portion 22 b is an oxide film as an antioxidant layer.The second shell portion 22 b contains α iron oxide, aluminum oxide, orsilicon oxide. α-iron oxide can contain, for example, at least one ironoxide of Fe₃O₄, Fe₂O₃, and FeO. In a case where the first shell portion22 a contains α-Fe (soft magnetic material), α-iron oxide may beobtained by oxidizing α-Fe contained in the first shell portion 22 a.

By inclusion of the first shell portion 22 a in the ε iron oxideparticle as described above, thermal stability can be secured. As aresult, the coercive force He of the entire ε iron oxide particles(core-shell particles) can be adjusted to a coercive force He suitablefor recording while the coercive force He of the core portion 21 aloneis maintained at a large value. Furthermore, by inclusion of the secondshell portion 22 b in the ε iron oxide particle as described above, itis possible to suppress deterioration of the characteristics of the εiron oxide particles due to generation of a rust or the like on surfacesof the particles by exposure of the ε iron oxide particles to the airduring a step of manufacturing the magnetic recording medium 10 andbefore the step. Therefore, characteristic deterioration of the magneticrecording medium 10 can be suppressed.

The ε iron oxide particle may have a shell portion 23 having a singlelayer structure as illustrated in FIG. 6 . In this case, the shellportion 23 has a similar configuration to the first shell portion 22 a.However, the ε iron oxide particle preferably has a two-layered shellportion 22 from a viewpoint of suppressing characteristic deteriorationof the ε iron oxide particle.

The ε iron oxide particle may contain an additive instead of thecore-shell structure, or may contain an additive while having thecore-shell structure. In these cases, some of Fe atoms in the ε ironoxide particles are replaced with an additive. Even by inclusion of anadditive in the ε iron oxide particle, the coercive force He of theentire ε iron oxide particles can be adjusted to a coercive force Hesuitable for recording. Therefore, recordability can be improved. Theadditive is a metal element other than iron, preferably a trivalentmetal element, and more preferably at least one selected from the groupincluding aluminum (Al), gallium (Ga), and indium (In).

Specifically, the ε iron oxide containing an additive is anε-Fe_(2-x)M_(x)O₃ crystal (in which M represents a metal element otherthan iron, preferably a trivalent metal element, and more preferably atleast one of Al, Ga, or In, and x satisfies, for example, 0<x<1).

The average particle size (average maximum particle size) of themagnetic powder is preferably 22 nm or less, more preferably 8 nm ormore and 22 nm or less, and still more preferably 12 nm or more and 22nm or less. In the magnetic recording medium 10, an area having a halfsize of a recording wavelength is an actual magnetization area.Therefore, by setting the average particle size of the magnetic powderto a half or less of the shortest recording wavelength, it is possibleto obtain good S/N. Therefore, when the average particle size of themagnetic powder is 22 nm or less, in the magnetic recording medium 10having a high recording density (for example, the magnetic recordingmedium 10 that can record a signal at the shortest recording wavelengthof 44 nm or less), good electromagnetic conversion characteristics (forexample, SNR) can be obtained. Meanwhile, when the average particle sizeof the magnetic powder is 8 nm or more, dispersibility of the magneticpowder is further improved, and better electromagnetic conversioncharacteristics (for example, SNR) can be obtained.

The average aspect ratio of the magnetic powder is preferably 1.0 ormore and 3.5 or less, more preferably 1.0 or more and 3.1 or less, andstill more preferably 1.0 or more and 2.5 or less. When the averageaspect ratio of the magnetic powder is within a range of 1.0 or more and3.5 or less, aggregation of the magnetic powder can be suppressed, andresistance applied to the magnetic powder can be suppressed when themagnetic powder is perpendicularly oriented in a step of forming themagnetic layer 13. Therefore, perpendicular orientation of the magneticpowder can be improved.

In a case where the magnetic powder contains ε iron oxide particles, theaverage particle size and average aspect ratio of the magnetic powderare determined as follows.

First, the magnetic recording medium 10 to be measured is processed tobe thinned by a focused ion beam (FIB) method and the like. In a casewhere the FIB method is used, as a pretreatment for observing a TEMimage of a cross section described later, a carbon film and a tungstenthin film are formed as protective films. The carbon film is formed onthe magnetic layer side surface and the back layer side surface of themagnetic recording medium 10 by a vapor deposition method, and thetungsten thin film is further formed on the magnetic layer side surfaceby a vapor deposition method or a sputtering method. Thinning isperformed in a length direction (longitudinal direction) of the magneticrecording medium 10. That is, by the thinning, a cross section parallelto both the longitudinal direction and the thickness direction of themagnetic recording medium 10 is formed.

Cross-sectional observation is performed for the cross section of theobtained thin sample such that the entire magnetic layer 13 is includedwith respect to the thickness direction of the magnetic layer 13 using atransmission electron microscope (H-9500 manufactured by HitachiHigh-Technologies) with an acceleration voltage of 200 kV and an overallmagnification of 500,000 times, and a TEM photograph is imaged.

Next, 50 particles the shapes of which can be clearly confirmed areselected from the imaged TEM photograph, and the long axis length DL andthe short axis length DS of each of the particles are measured. Here,the long axis length DL means the largest distance among distancesbetween two parallel lines drawn from all angles so as to come intocontact with an outline of each of the particles (so-called maximumFeret diameter). Meanwhile, the short axis length DS means the largestlength among the lengths of a particle in a direction orthogonal to thelong axis (DL) of the particle.

Subsequently, the long axis lengths DL of the measured 50 particles aresimply averaged (arithmetically averaged) to determine an average longaxis length DL_(ave). The average long axis length DL_(ave) determinedin this manner is taken as an average particle size of the magneticpowder. Furthermore, the short axis lengths DS of the measured 50particles are simply averaged (arithmetically averaged) to determine anaverage short axis length DS_(ave). Then, an average aspect ratio(DL_(ave)/DS_(ave)) of the particles is determined from the average longaxis length DL_(ave) and the average short axis length DS_(ave).

The average particle volume of the magnetic powder is preferably 5500nm³ or less, more preferably 270 nm³ or more and 5500 nm³ or less, andstill more preferably 900 nm³ or more and 5500 nm³ or less. When theaverage particle volume of the magnetic powder is 5500 nm³ or less, asimilar effect to that in a case where the average particle size of themagnetic powder is 22 nm or less can be obtained. Meanwhile, when theaverage particle volume of the magnetic powder is 270 nm³ or more, asimilar effect to a case where the average particle size of the magneticpowder is 8 nm or more can be obtained.

In a case where the ε iron oxide particle has a spherical shape or asubstantially spherical shape, the average particle volume of themagnetic powder is determined as follows. First, an average long axislength DL_(ave) is determined in a similar manner to the above methodfor calculating the average particle size of the magnetic powder. Next,an average volume V of the magnetic powder is determined by thefollowing formula.V=(π/6)×DL _(ave) ³

In a case where the ε iron oxide particle has a cubic shape, the averagevolume of the magnetic powder is determined as follows.

The magnetic recording medium 10 is processed to be thinned by a focusedion beam (FIB) method and the like. In a case where the FIB method isused, as a pretreatment for observing a TEM image of a cross sectiondescribed later, a carbon film and a tungsten thin film are formed asprotective films. The carbon film is formed on the magnetic layer sidesurface and the back layer side surface of the magnetic recording medium10 by a vapor deposition method, and the tungsten thin film is furtherformed on the magnetic layer side surface by a vapor deposition methodor a sputtering method. The thinning is performed in a length direction(longitudinal direction) of the magnetic recording medium 10. That is,by the thinning, a cross section parallel to both the longitudinaldirection and the thickness direction of the magnetic recording medium10 is formed.

Cross-sectional observation is performed for the obtained thin samplesuch that the entire magnetic layer 13 is included with respect to thethickness direction of the magnetic layer 13 using a transmissionelectron microscope (H-9500 manufactured by Hitachi High-Technologies)with an acceleration voltage of 200 kV and an overall magnification of500,000 times, and a TEM photograph is obtained. Note that themagnification and the acceleration voltage may be appropriately adjustedaccording to the type of device.

Next, 50 particles the shapes of which are clear are selected from theimaged TEM photograph, and the side length DC of each of the particlesis measured. Subsequently, the side lengths DC of the measured 50particles are simply averaged (arithmetically averaged) to determine anaverage side length DC_(ave). Next, the average volume V_(ave) (particlevolume) of the magnetic powder is determined from the following formulausing the average side length DC_(ave).V _(ave) =DC _(ave) ³

(Embodiment in which Magnetic Powder Contains Co-Containing SpinelFerrite)

According to still another preferred embodiment of the presenttechnology, the magnetic powder can contain powder of nanoparticlescontaining Co-containing spinel ferrite (hereinafter also referred to as“cobalt ferrite particles”). That is, the magnetic powder can be cobaltferrite magnetic powder. The cobalt ferrite particle preferably hasuniaxial crystal anisotropy. The cobalt ferrite magnetic particle has,for example, a cubic shape or a substantially cubic shape. TheCo-containing spinel ferrite may further contain at least one selectedfrom the group including Ni, Mn, Al, Cu, and Zn in addition to Co.

Cobalt ferrite has, for example, an average composition represented bythe following formula (1).Co_(x)M_(y)Fe₂O_(z)  (1)

(Provided that in formula (1), M represents one or more metals selectedfrom the group including Ni, Mn, Al, Cu, and Zn, for example. xrepresents a value within a range of 0.4≤x≤1.0. y represents a valuewithin a range of 0≤y≤0.3. Provided that x and y satisfy a relationshipof (x+y)≤1.0. z represents a value within a range of 3≤z≤4. Some of Featoms may be replaced with another metal element.)

The average particle size of the cobalt ferrite magnetic powder ispreferably 25 nm or less, and more preferably 23 nm or less. Thecoercive force He of the cobalt ferrite magnetic powder is preferably2500 Oe or more, and more preferably 2600 Oe or more and 3500 Oe orless.

In a case where the magnetic powder contains powder of cobalt ferriteparticles, the average particle size of the magnetic powder ispreferably 25 nm or less, and more preferably 10 nm or more and 23 nm orless. When the average particle size of the magnetic powder is 25 nm orless, good electromagnetic conversion characteristics (for example, SNR)can be obtained in the magnetic recording medium 10 having a highrecording density. Meanwhile, when the average particle size of themagnetic powder is 10 nm or more, dispersibility of the magnetic powderis further improved, and better electromagnetic conversioncharacteristics (for example, SNR) can be obtained. In a case where themagnetic powder contains powder of cobalt ferrite particles, the averageaspect ratio and average particle size of the magnetic powder aredetermined by the same method as that in a case where the magneticpowder contains ε iron oxide particles.

The average particle volume of the magnetic powder is preferably 15000nm³ or less, and more preferably 1000 nm³ or more and 12000 nm³ or less.When the average particle volume of the magnetic powder is 15000 nm³ orless, a similar effect to that in a case where the average particle sizeof the magnetic powder is 25 nm or less can be obtained. Meanwhile, whenthe average particle volume of the magnetic powder is 1000 nm³ or more,a similar effect to a case where the average particle size of themagnetic powder is 10 nm or more can be obtained. Note that the averageparticle volume of the magnetic powder is determined by the samecalculation method as that in a case where the ε iron oxide particle hasa cubic shape.

(Lubricant)

The magnetic layer includes a lubricant. The lubricant may be, forexample, one or more selected from fatty acids and/or fatty acid esters,and preferably includes both a fatty acid and a fatty acid ester.Inclusion of the lubricant in the magnetic layer, particularly inclusionof both a fatty acid and a fatty acid ester in the magnetic layercontributes to improvement in traveling stability of the magneticrecording medium. More particularly, inclusion of the lubricant in themagnetic layer and presence of pores in the magnetic layer achieve goodtraveling stability. The improvement in the traveling stability isconsidered to be because the coefficient of dynamic friction of themagnetic layer side surface of the magnetic recording medium is adjustedto a value suitable for traveling of the magnetic recording medium bythe lubricant.

The fatty acid may preferably be a compound represented by the followinggeneral formula (1) or (2). For example, the lubricant may contain, asthe fatty acid, one or both of a compound represented by the followinggeneral formula (1) and a compound represented by the general formula(2).

Furthermore, the fatty acid ester may preferably be a compoundrepresented by the following general formula (3) or (4). For example,the lubricant may contain, as the fatty acid ester, one or both of acompound represented by the following general formula (3) and a compoundrepresented by the general formula (4).

By inclusion of one or both of a compound represented by general formula(1) and a compound represented by general formula (2), and inclusion ofone or both of a compound represented by general formula (3) and acompound represented by general formula (4) in the lubricant, anincrease in the coefficient of dynamic friction due to repeatedrecording or reproduction in the magnetic recording medium can besuppressed.CH₃(CH₂)_(k)COOH  (1)

(Provided that in the general formula (1), k is an integer selected froma range of 14 or more and 22 or less, more preferably a range of 14 ormore and 18 or less)CH₃(CH₂)_(n)CH═CH(CH₂)_(m)COOH  (2)

(Provided that in the general formula (2), the sum of n and m is aninteger selected from a range of 12 or more and 20 or less, morepreferably a range of 14 or more and 18 or less)CH₃(CH₂)_(p)COO(CH₂)_(q)CH₃  (3)

(Provided that in the general formula (3), p is an integer selected froma range of 14 or more and 22 or less, more preferably a range of 14 ormore and 18 or less, and q is an integer selected from a range of 2 ormore and 5 or less, more preferably a range of 2 or more and 4 or less)CH₃(CH₂)_(r)COO—(CH₂)_(s)CH(CH₃)₂  (4)

(Provided that in the general formula (4), r is an integer selected froma range of 14 or more and 22 or less, and s is an integer selected froma range of 1 or more and 3 or less.)

(Binder)

As the binder, a resin having a structure in which a polyurethane-basedresin, a vinyl chloride-based resin, or the like has been subjected to acrosslinking reaction is preferable. However, the binder is not limitedto these resins, and other resins may be blended appropriately accordingto physical properties and the like required for the magnetic recordingmedium 10. Usually, a resin to be blended is not particularly limited aslong as being generally used in the application type magnetic recordingmedium 10.

As the binder, for example, one or a combination of two or more selectedfrom polyvinyl chloride, polyvinyl acetate, a vinyl chloride-vinylacetate copolymer, a vinyl chloride-vinylidene chloride copolymer, avinyl chloride-acrylonitrile copolymer, an acrylate-acrylonitrilecopolymer, an acrylate-vinyl chloride-vinylidene chloride copolymer, anacrylate-vinylidene chloride copolymer, a methacrylate-vinylidenechloride copolymer, a methacrylate-vinyl chloride copolymer, amethacrylate-ethylene copolymer, polyvinyl fluoride, a vinylidenechloride-acrylonitrile copolymer, an acrylonitrile-butadiene copolymer,a polyamide resin, polyvinyl butyral, a cellulose derivative (celluloseacetate butyrate, cellulose diacetate, cellulose triacetate, cellulosepropionate, and nitrocellulose), a styrene-butadiene copolymer, apolyester resin, an amino resin, and a synthetic rubber can be used.

Furthermore, a thermosetting resin or a reactive resin may be used asthe binder. Examples of the thermosetting resin or the reactive resininclude a phenol resin, an epoxy resin, a urea resin, a melamine resin,an alkyd resin, a silicone resin, a polyamine resin, and a ureaformaldehyde resin.

Furthermore, in order to improve dispersibility of the magnetic powder,a polar functional group such as —SO₃M, —OSO₃M, —COOM, or P═O(OM)₂ maybe introduced into each of the above-described binders. Here, in theformulae, M represents a hydrogen atom or an alkali metal such aslithium, potassium, or sodium.

Moreover, examples of the polar functional group include a side chaintype group having a terminal group of —NR1R2 or —NR1R2R3⁺X⁻, and a mainchain type group of >NR1R2⁺X⁻. Here, R1, R2, and R3 in the formula eachindependently represent a hydrogen atom or a hydrocarbon group, and X⁻represents an ion of a halogen element such as fluorine, chlorine,bromine, or iodine, or an inorganic or organic ion. Furthermore,examples of the polar functional group include —OH, —SH, —CN, and anepoxy group.

(Additive)

As nonmagnetic reinforcing particles, the magnetic layer 13 may furthercontain aluminum oxide (α, β, or γ alumina), chromium oxide, siliconoxide, diamond, garnet, emery, boron nitride, titanium carbide, siliconcarbide, titanium carbide, titanium oxide (rutile type or anatase typetitanium oxide), and the like.

(Underlayer)

The underlayer 12 is a nonmagnetic layer containing nonmagnetic powderand a binder as main components. The underlayer 12 further contains alubricant. The description regarding the binder and lubricant containedin the magnetic layer 13 described above also applies to the binder andlubricant contained in the underlayer 12. The underlayer 12 may furthercontain at least one additive selected from conductive particles, acuring agent, a rust preventive, and the like as necessary.

The underlayer 12 has an average thickness of 0.5 μm or more and 0.9 μmor less. The average thickness of the underlayer 12 may be preferably0.88 μm or less, more preferably 0.85 μm or less, and still morepreferably 0.80 μm or less. Furthermore, the average thickness of theunderlayer 12 may be preferably 0.52 μm or more, more preferably 0.55 μmor more, and still more preferably 0.60 μm or more. Note that theaverage thickness of the underlayer 12 is determined in a similar mannerto the average thickness t_(m) of the magnetic layer 13. However, amagnification of a TEM image is appropriately adjusted according to thethickness of the underlayer 12.

The underlayer 12 may have pores, that is, the underlayer 12 may have alarge number of pores. The pores of the underlayer 12 may be formed, forexample, along with formation of pores in the magnetic layer 13, and inparticular, can be formed by pressing a large number of protrusionsformed on the back layer side surface of the magnetic recording medium10 against the magnetic layer side surface. That is, by forming a recesscorresponding to the shape of a protrusion on the magnetic layer sidesurface, pores can be formed in the magnetic layer 13 and the underlayer12.

Furthermore, pores may be formed as a solvent volatilizes in a step ofdrying a magnetic layer forming coating material. Furthermore, when themagnetic layer forming coating material is applied to a surface of theunderlayer 12 in order to form the magnetic layer 13, a solvent in themagnetic layer forming coating material passes through the pores of theunderlayer 12 formed when the lower layer is applied and dried, and canpermeate the underlayer 12. Thereafter, when the solvent that haspermeated the underlayer 12 volatilizes in a step of drying the magneticlayer 13, the solvent that has permeated the underlayer 12 moves fromthe underlayer 12 to the surface of the magnetic layer 13, thereby poresmay be formed. The pores formed in this way can communicate, forexample, the magnetic layer 13 with the underlayer 12. The averagediameter of the pores can be adjusted by changing the solid content ofthe magnetic layer forming coating material or the type of a solventthereof and/or drying conditions of the magnetic layer forming coatingmaterial.

By forming pores in both the magnetic layer 13 and the underlayer 12, aparticularly suitable amount of lubricant for good traveling stabilityappears on the magnetic layer side surface, and an increase in thecoefficient of dynamic friction due to repeated recording orreproduction can be further suppressed.

(Nonmagnetic Powder)

The nonmagnetic powder contained in the underlayer 12 can contain, forexample, at least one selected from inorganic particles and organicparticles. One kind of nonmagnetic powder may be used singly, or two ormore kinds of nonmagnetic powder may be used in combination. Theinorganic particles include, for example, one or a combination of two ormore selected from a metal, a metal oxide, a metal carbonate, a metalsulfate, a metal nitride, a metal carbide, and a metal sulfide. Morespecifically, the inorganic particles can be one or more selected from,for example, iron oxyhydroxide, hematite, titanium oxide, and carbonblack. Examples of the shape of the nonmagnetic powder include variousshapes such as an acicular shape, a spherical shape, a cubic shape, anda plate shape, but are not limited thereto.

(Back Layer)

The back layer 14 can contain a binder and nonmagnetic powder. The backlayer 14 may contain various additives such as a lubricant, a curingagent, and an antistatic agent as necessary. The above descriptionregarding the binder and nonmagnetic powder contained in the underlayer12 also applies to the binder and nonmagnetic powder contained in theback layer 14.

The average thickness tb of the back layer 14 satisfies preferablytb≤0.6 μm, more preferably tb≤0.5 μm. By setting the average thicknesstb of the back layer 14 within the above range, even in a case where theaverage thickness t_(T) of the magnetic recording medium 10 satisfiest_(T)≤5.6 μm, the thicknesses of the underlayer 12 and the base layer 11can be kept large. This makes it possible to maintain travelingstability of the magnetic recording medium 10 in therecording/reproducing device.

The average thickness tb of the back layer 14 is determined as follows.First, the average thickness t_(T) of the magnetic recording medium 10is measured. A method for measuring the average thickness t_(T) is asdescribed in “(3) Physical properties and structure” below.Subsequently, the back layer 14 of the sample is removed with a solventsuch as methyl ethyl ketone (MEK) or dilute hydrochloric acid. Next, thethickness of the sample is measured at five or more points using a laserhologage (LGH-110C) manufactured by Mitutoyo Corporation, and themeasured values are simply averaged (arithmetically averaged) tocalculate an average thickness t_(B) [μm]. Thereafter, the averagethickness t_(b) (μm) of the back layer 14 is determined by the followingformula. Note that the measurement points are randomly selected from thesample.t _(b)[μm]=t _(T)[μm]−t _(B)[μm]

Here, a value calculated by the measuring device is described to thefirst decimal place by rounding off the second decimal place.

Out of the two surfaces of the back layer 14, the surface forming theback layer side surface of the magnetic recording medium 10 preferablyhas a large number of protrusions. By winding the magnetic recordingmedium 10 in a roll shape, the large number of protrusions can form alarge number of pores in the magnetic layer 13.

The protrusions can be formed, for example, by inclusion of particles inthe back layer forming coating material. The particles can be inorganicparticles such as carbon black, for example. The particle diameters ofthe particles can be appropriately selected according to the sizes ofthe pores to be formed in the magnetic layer 13.

The average particle size of particles (particularly inorganicparticles) contained in the back layer 14 is preferably 10 nm or moreand 150 nm or less, and more preferably 15 nm or more and 110 nm orless. The average particle size of the inorganic particles can bedetermined in a similar manner to an average particle size of the aboveε iron oxide magnetic powder.

(3) Physical Properties and Structure

(Amount of Width Change)

The amount of dimensional change of the magnetic recording medium 10 ina width direction thereof between a state in which a tension of 0.5 N isapplied to the magnetic recording medium in a longitudinal directionthereof and a state in which a tension of 1.0 N is applied to themagnetic recording medium in the longitudinal direction (hereinafterreferred to as the amount of width change) can be preferably 4.0 ormore, more preferably 4.1 μm or more, and still more preferably 4.2 μmor more. Furthermore, the amount of width change may be preferably 6.0μm or less, for example, 5.0 μm or less. The amount of width change canbe, for example, 4.0 μm or more and 6.0 μm or less, and particularly 4.2μm or more and 6.0 μm or less.

The amount of width change within the above range improves ease ofdimensional adjustment in the width direction by adjusting a tensionapplied to the magnetic recording medium 10 in a longitudinal directionthereof (hereinafter, also referred to as controllability of thedimensions in the width direction or width controllability).

The dimensions of the magnetic recording medium 10 in a width directionthereof can change after its manufacture due to an elapse of time(particularly due to long-term storage) and/or a change in environmentaround the magnetic recording medium 10 (for example, temperature and/orhumidity). Although the dimensional change in the width direction isvery small, the dimensional change can affect a magnetic recordingmedium having a narrow servo bandwidth and/or data bandwidth in order toimprove recording density. For example, a dimensional change in thewidth direction may cause a phenomenon undesirable for magneticrecording, such as an off-track phenomenon. Therefore, theabove-described recording/reproducing device for adjusting the width ofthe magnetic recording medium by adjusting a tension of the magneticrecording medium in a longitudinal direction thereof can be used. Theamount of width change within the above range makes it easy to adjustthe dimensions in the width dimension by the recording/reproducingdevice, for example. Note that the off-track phenomenon means that atarget track does not exist at a track position to be read by themagnetic head, or the magnetic head reads a wrong track position.

The amount of width change can be measured as follows.

First, the magnetic recording medium 10 having a width of ½ inches isprepared and cut into a length of 250 mm to manufacture a sample 10S.Next, a load is applied to the sample 10S in a longitudinal directionthereof in the order of 0.5 N and 1.0 N, and the widths Wa and Wb of thesample 10S in a case where loads of 0.5 N and 1.0 N are applied aremeasured, respectively. A difference between measured Wa and Wb (Wa−Wb)is defined as the amount of width change when a load of 0.5 N isadditionally applied.

The width of the sample 10S when each load is applied is measured asfollows. First, a measuring device incorporating a digital dimensionmeasuring instrument LS-7000 manufactured by Keyence Corporation,illustrated in FIG. 11A, is prepared as a measuring device, and thesample 10S is set in this measuring device. Specifically, one end of thelong sample (magnetic recording medium) 10S is fixed by a fixing portion231. Next, as illustrated in FIG. 11A, the sample 10S is placed on fivesubstantially cylindrical and rod-shaped support members 232. The sample10S is placed on the five support members 232 such that the back surfacethereof comes into contact with the support members 232. The fivesupport members 232 (particularly surfaces thereof) all containstainless steel SUS304, and have a surface roughness Rz (maximum height)of 0.15 μm to 0.3 μm.

Disposition of the five rod-shaped support members 232 will be describedwith reference to FIG. 11B. As illustrated in FIG. 11B, the sample 10Sis placed on the five support members 232. Hereinafter, the five supportmembers 232 will be referred to as “first support member”, “secondsupport member”, “third support member” (having a slit 232A), “fourthsupport member”, and “fifth support member” (closest to a weight 233)from a side closest to the fixing portion 231. Each of these fivesupport members has a diameter of 7 mm. A distance d1 between the firstsupport member and the second support member (in particular, a distancebetween the centers of these support members) is 20 mm. A distance d2between the second support member and the third support member is 30 mm.A distance d3 between the third support member and the fourth supportmember is 30 mm. A distance d4 between the fourth support member and thefifth support member is 20 mm. Furthermore, the three support members ofthe second to fourth support members are disposed such that portions ofthe sample 10S between the second support member and the third supportmember and between the third support member and the fourth supportmember form a plane substantially perpendicular to the direction ofgravity. Furthermore, the first support member and the second supportmember are disposed such that the sample 10S forms an angle of θ1=30°with respect to the substantially perpendicular plane between the firstsupport member and the second support member. Moreover, the fourthsupport member and the fifth support member are disposed such that thesample 10S forms an angle of θ2=30° with respect to the substantiallyperpendicular plane between the fourth support member and the fifthsupport member.

Furthermore, among the five support members 232, the third supportmember is fixed so as not to rotate, but the other four support membersare all rotatable.

The sample 10S is held so as not to move in a width direction of thesample 10S on the support members 232. Note that among the supportmembers 232, the support member 232 located between a light emitter 234and a light receiver 235 and located substantially at the center betweenthe fixing portion 231 and a portion to which a load is applied has theslit 232A. Light L is emitted from the light emitter 234 to the lightreceiver 235 through the slit 232A. The slit 232A has a slit width of 1mm, and the light L can pass through the width without being blocked bya frame of the slit 232A.

Subsequently, the measuring device is housed in a chamber controlledunder a constant environment in which the temperature is 25° C. and therelative humidity is 50%. Thereafter, the weight 233 for applying a loadof 0.5 N is attached to the other end of the sample 10S, and the sample10S is left in the above environment for two hours. After being left fortwo hours, the width Wa of the sample 10S is measured. Next, the weightfor applying a load of 0.5 N is changed to a weight for applying a loadof 1.0 N, and the width Wb of the sample 10S is measured five minutesafter the change.

As described above, by adjusting the weight of the weight 233, a loadapplied to the sample 10S in a longitudinal direction thereof can bechanged. With each load applied, the light L is emitted from the lightemitter 234 toward the light receiver 235, and the width of the sample10S to which the load is applied in a longitudinal direction thereof ismeasured. The measurement of the width is performed in a state where thesample 10S is not curled. The light emitter 234 and the light receiver235 are included in the digital dimension measuring instrument LS-7000.

(Average Thickness t_(T) of Magnetic Recording Medium)

The average thickness t_(T) of the magnetic recording medium 10satisfies t_(T)≤5.6 μm, and can be more preferably 5.3 μm or less, andstill more preferably 5.2 μm or less, 5.0 μm or less, or 4.6 μm or less.When the average thickness t_(T) of the magnetic recording medium 10 iswithin the above numerical range (for example, by satisfying t_(T)≤5.6μm), the recording capacity that can be recorded in one data cartridgecan be increased as compared with a conventional case. A lower limitvalue of the average thickness t_(T) of the magnetic recording medium 10is not particularly limited, but satisfies, for example, 3.5 μm≤t_(T).

The average thickness t_(T) of the magnetic recording medium 10 isdetermined as follows. First, the magnetic recording medium 10 having awidth of ½ inches is prepared and cut into a length of 250 mm tomanufacture a sample. Next, the thickness of the sample is measured atfive or more points using a laser hologage (LGH-110C) manufactured byMitutoyo Corporation as a measuring device, and the measured values aresimply averaged (arithmetically averaged) to calculate an averagethickness t_(T) [μm]. Note that the measurement points are randomlyselected from the sample. Here, a value calculated by the measuringdevice is described to the first decimal place by rounding off thesecond decimal place.

(Young's Modulus of Magnetic Recording Medium in Longitudinal Direction)

The Young's modulus of the magnetic recording medium 10 in alongitudinal direction thereof is 7.90 GPa or less, more preferably 7.85or less, and still more preferably 7.80 GPa or less. The above Young'smodulus may be, for example, 3.00 GPa or more, preferably 4.00 Gpa ormore, more preferably 5.00 Gpa or more, still more preferably 6.00 GPaor more, and further still more preferably 7.00 GPa or more. Since theYoung's modulus is within the numerical range described above, themagnetic recording medium 10 is suitable for use in arecording/reproducing device that keeps the width of the magneticrecording medium constant or substantially constant by adjusting atension of the magnetic recording medium 10 in a longitudinal directionthereof. The recording/reproducing device can detect, for example,dimensions or a dimensional change of the magnetic recording medium in awidth direction thereof, and can adjust the tension in the longitudinaldirection on the basis of a detection result.

The Young's modulus of the magnetic recording medium 10 in alongitudinal direction thereof can be measured as follows.

The above Young's modulus is measured using a tensile tester(manufactured by Shimadzu Corporation, AG-100D).

First, the magnetic recording medium 10 having a width of ½ inches iscut into a length of 180 mm to prepare a measurement sample. Two jigsthat can fix the measurement sample so as to cover the entire widththereof are attached to the above tensile tester. Two ends in the lengthdirection of the measurement sample are chucked by the two jigs,respectively. A distance between the chucks is set to 100 mm. After themeasurement sample is chucked, a stress is gradually applied such thatthe measurement sample is pulled in the length direction. The pullingspeed is set to 0.1 mm/min. From the change in stress and the amount ofelongation at this time, the Young's modulus is calculated using thefollowing formula.E={(ΔN/S)/(Δx/L)}×10⁶

In the formula described above, E represents Young's modulus (N/m²), ΔNrepresents a change in stress (N), S represents the cross-sectional areaof a measurement sample (mm²) Δx represents the amount of elongation(mm), and L represents a distance between the two jigs (distance betweenchucks) (mm).

The stress when the measurement sample is pulled by the tensile testerdescribed above is changed from 0.5 N to 1.0 N. The change in stress(ΔN) and the amount of elongation (Δx) when the stress is changed inthis way are used for the calculation by the formula described above.

(Coating Film Thickness/Base Thickness)

In the magnetic recording medium 10, the ratio of the total thickness ofthe magnetic layer, the underlayer, and the back layer to the thicknessof the base layer (hereinafter referred to as coating filmthickness/base thickness) is preferably 0.38 or less, more preferably0.34 or less, still more preferably 0.32 or less, and further still morepreferably 0.30 or less.

The coating film thickness/base thickness is preferably 0.20 or more,more preferably 0.22 or more, and still more preferably 0.24 or more.

Since the coating film thickness/base thickness is within the numericalrange described above, the magnetic recording medium 10 is more suitablefor use in a recording/reproducing device that keeps the width of themagnetic recording medium constant or substantially constant byadjusting a tension of the magnetic recording medium in a longitudinaldirection thereof.

In general, the Young's modulus of the coating film (magnetic layer,underlayer, and back layer) is higher than that of the base layer. Bysetting the coating film thickness/base thickness within the abovenumerical range, the Young's modulus of the magnetic recording medium 10in a longitudinal direction thereof can be adjusted to be suitable foruse in the recording/reproducing device. Note that the coating filmthickness is a value obtained by adding the thickness of the magneticlayer, the thickness of the underlayer, and the thickness of the backlayer.

Note that the present technology also provides a tape-shaped magneticrecording medium including: a magnetic layer; an underlayer; a baselayer; and a back layer, in which the underlayer has a thickness of 0.5μm or more and 0.9 μm or less, the magnetic recording medium has anaverage thickness t_(T) of 5.6 μm or less, the magnetic recording mediumincludes a lubricant, the magnetic recording medium has pores, the poreshave an average diameter of 6 nm or more and 11 nm or less, and theratio of the total thickness of the magnetic layer, the underlayer, andthe back layer to the thickness of the base layer is 0.38 or less.

(Average Diameter of Pores of Magnetic Recording Medium)

The average diameter of the pores of the magnetic recording medium 10(pore diameter of maximum pore volume at the time of desorption) is 6 nmor more and 11 nm or less, preferably 6 nm or more and 10 nm or less,more preferably 6.5 nm or more and 10 nm or less, and still morepreferably 7 nm or more and 9 nm or less in a state where the lubricanthas been removed from the magnetic recording medium 10 and the magneticrecording medium 10 has been dried. The average pore volume within thenumerical range described above can further improve the effect ofsuppressing the increase in the coefficient of dynamic friction afterrepeated recording or reproduction is performed.

The average diameter of the pores formed in the magnetic recordingmedium 10 (pore diameter of maximum pore volume at the time ofdesorption) is measured in a state where the lubricant has been removedfrom the magnetic recording medium and the magnetic recording medium hasbeen dried. Specifically, the measurement is performed as follows.

First, the magnetic recording medium 10 having a size about 10% largerthan the area 0.1265 m² is immersed in hexane (amount in which the tapecan be sufficiently immersed, for example, 150 mL) for 24 hours, thennaturally dried, and cut out so as to have an area of 0.1265 m² (forexample, 50 cm at each end of the dried tape is cut off to prepare atape having a width of 10 m) to manufacture a measurement sample. Thelubricant is removed from the magnetic recording medium 10 by immersionin the hexane for 24 hours, and the magnetic recording medium 10 isdried by the natural drying.

Next, the average diameter of the pores is measured by a BJH methodusing a specific surface area/pore distribution measuring device. Ameasuring device and measuring conditions are indicated below. In thisway, the average diameter of the pores is measured.

Measurement environment: room temperature

Measuring device: 3 FLEX manufactured by Micromeritics Instrument Corp.

Measurement adsorbate: N2 gas

Measurement pressure range (P/P⁰): 0 to 0.995

For the measurement pressure range, the pressure is changed asillustrated in Table below. The pressure values in the following Tableare relative pressures P/P⁰. In the following Table, for example, instep 1, the pressure is changed so as to change by 0.001 per 10 secondsfrom a starting pressure 0.000 to an ultimate pressure 0.010. When thepressure reaches the ultimate pressure, pressure change in the next stepis performed. The similar applies to steps 2 to 10. However, in eachstep, in a case where the pressure has not reached equilibrium, thedevice waits for the pressure to reach equilibrium and then proceeds tothe next step.

Starting Pressure Ultimate Step pressure change pressure 1 0.0000.001/10 sec  0.010 2 0.010 0.02/10 sec 0.100 3 0.100 0.05/10 sec 0.6004 0.600 0.05/10 sec 0.950 5 0.950 0.05/10 sec 0.990 6 0.990 0.05/10 sec0.995 7 0.995 0.01/10 sec 0.990 8 0.990 0.01/10 sec 0.950 9 0.9500.05/10 sec 0.600 10 0.600 0.05/10 sec 0.300

(Friction Coefficient Ratio (μ_(B)/μ_(A)))

The magnetic recording medium 10 has a friction coefficient ratio(μ_(B)/μ_(A)) of preferably 1.0 to 2.0, more preferably 1.0 to 1.8,still more preferably 1.0 to 1.6, in which A represents a coefficient ofdynamic friction between a magnetic layer side surface of the magneticrecording medium and a magnetic head in a state where a tension of 0.4 Nis applied in the longitudinal direction of the magnetic recordingmedium 10, and μ_(B) represents a coefficient of dynamic frictionbetween the magnetic layer side surface of the magnetic recording mediumand the magnetic head in a state where a tension of 1.2 N is applied inthe longitudinal direction of the magnetic recording medium. Thefriction coefficient ratio (μ_(B)/μ_(A)) within the above numericalrange can reduce a change in the coefficient of dynamic friction due tothe tension fluctuation during traveling, and therefore can stabilizetraveling of the magnetic recording medium 10.

The coefficients of dynamic friction μA and μ_(B) for calculating thefriction coefficient ratio (μ_(B)/μ_(A)) are determined as follows.

First, as illustrated in FIG. 7(a), the magnetic recording medium 10having a width of ½ inches is placed on two cylindrical guide rolls 73-1and 73-2 each having a diameter of one inch and disposed in parallel toand spaced apart from each other such that the magnetic surface is incontact with the guide rolls 73-1 and 73-2. The two guide rolls 73-1 and73-2 are fixed to a hard plate-shaped member 76, and thereby have afixed positional relationship with each other.

Subsequently, the magnetic recording medium 10 is brought into contactwith a head block (for recording/reproducing) 74 mounted on an LTO5drive such that the magnetic surface is in contact with the head block74 and a holding angle θ₁(°) is 5.6°. The head block 74 is disposedsubstantially at the center of the guide rolls 73-1 and 73-2. The headblock 74 is movably attached to the plate-shaped member 76 such that theholding angle θ1 can be changed. When the holding angle θ₁(°) becomes5.6°, the position of the head block 74 is fixed to the plate-shapedmember 76. As a result, a positional relationship between the guiderolls 73-1 and 73-2 and the head block 74 is also fixed.

One end of the magnetic recording medium 10 is connected to a movablestrain gauge 71 via a jig 72. The magnetic recording medium 10 is fixedto the jig 72 as illustrated in FIG. 7(b).

A weight 75 is connected to the other end of the magnetic recordingmedium 10. The weight 75 applies a tension T₀[N] of 0.4 N to themagnetic recording medium 10 in a longitudinal direction thereof. Themovable strain gauge 71 is fixed onto a base 77. A positionalrelationship between the base 77 and the plate-shaped member 76 is alsofixed. As a result, a positional relationship among the guide rolls 73-1and 73-2, the head block 74, and the movable strain gauge 71 is fixed.

With the movable strain gauge 71, the magnetic recording medium 10 isslid on the head block 74 by 60 mm such that the magnetic recordingmedium 10 moves toward the movable strain gauge 71 at 10 mm/s. An outputvalue (voltage) of the movable strain gauge 71 at the time of sliding isconverted into T [N] on the basis of a linear relationship (as describedlater) between an output value acquired in advance and a load. T [N] isacquired 13 times from the start of sliding to the end of sliding forthe 60 mm slide, and 11 values of T [N] excluding totally two times ofthe first and last times are simply averaged to obtain T_(ave) [N].

Thereafter, the coefficient of dynamic friction μ_(A) is determined bythe following formula.

$\mu_{A} = {\frac{1}{( {\theta_{1}\lbrack{^\circ}\rbrack} ) \times ( {\Pi/180} )} \times {\ln( \frac{T_{ave}\lbrack N\rbrack}{T_{0}\lbrack N\rbrack} )}}$

The linear relationship is obtained as follows. That is, an output value(voltage) of the movable strain gauge 71 is obtained for each of caseswhere a load of 0.4 N is applied to the movable strain gauge 71 and aload of 1.5 N is applied thereto. From the obtained two output valuesand the two loads, a linear relationship between the output value andthe load is obtained. Using the linear relationship, as described above,the output value (voltage) from the movable strain gauge 71 duringsliding is converted into T [N].

The coefficient of dynamic friction s is measured by the same method asthe method for measuring the coefficient of dynamic friction μ_(A)except that the tension T₀[N] applied to the other end is set to 1.2 N.

The friction coefficient ratio (μ_(B)/μ_(A)) is calculated from thecoefficients of dynamic friction μ_(A) and μ_(B) measured as describedabove.

(Friction Coefficient Ratio (μ_(C(1000))/μ_(C(5))))

The magnetic recording medium 10 has the friction coefficient ratio(μ_(C(1000))/μ_(C(5))) of preferably 1.0 to 2.0, more preferably 1.0 to1.8, still more preferably 1.0 to 1.6, in which μ_(C(5)) represents acoefficient of dynamic friction at the fifth reciprocation in a casewhere the magnetic recording medium in a state where a tension of 0.6 Nis applied to the magnetic recording medium in a longitudinal directionthereof is reciprocatedly slid five times on a magnetic head, andμ_(C(1000)) represents a coefficient of dynamic friction at the 1000threciprocation in a case where the magnetic recording medium isreciprocated 1000 times on the magnetic head. The friction coefficientratio (μ_(C(1000))/μ_(C(5))) within the above numerical range can reducea change in the coefficient of dynamic friction due to traveling manytimes, and therefore can stabilize traveling of the magnetic recordingmedium 10.

The coefficients of dynamic friction μ_(C(5)) and μ_(C(1000)) forcalculating the friction coefficient ratio (μ_(C(1000))/μ_(C(5))) aredetermined as follows.

The magnetic recording medium 10 is connected to the movable straingauge 71 in the same manner as the method for measuring the coefficientof dynamic friction μA except that the tension T₀[N] applied to theother end of the magnetic recording medium 10 is set to 0.6 N. Then, themagnetic recording medium 10 is slid 60 mm toward the movable straingauge at 10 mm/s with respect to the head block 74 (forward path) andslid 60 mm away from the movable strain gauge (return path). Thisreciprocating operation is repeated 1000 times. Among the 1000reciprocating operations, a strain gauge output value (voltage) isacquired 13 times from the start of sliding to the end of sliding forthe 60 mm slide in the fifth forward path, and the output value isconverted into T [N] on the basis of a linear relationship between anoutput value determined as described above for the coefficient ofdynamic friction μ_(A) and a load. Eleven values of T [N] excludingtotally two times of the first and last times are simply averaged todetermine T_(ave) [N]. The coefficient of dynamic friction μ_(C(5)) isdetermined by the following formula.

$\mu_{C{(5)}} = {\frac{1}{( {\theta_{1}\lbrack{^\circ}\rbrack} ) \times ( {\pi/180} )} \times {\ln( \frac{T_{ave}\lbrack N\rbrack}{T_{0}\lbrack N\rbrack} )}}$

Moreover, the coefficient of dynamic friction μ_(C(1000)) is determinedin a similar manner to the coefficient of dynamic friction μ_(C(5))except that measurement is performed for the 1000th forward path.

The friction coefficient ratio μ_(C(1000))/μ_(C(5)) is calculated fromthe coefficients of dynamic friction μ_(C(5)) and μ_(C(1000)) measuredas described above.

(Squareness Ratio S2 Measured in Perpendicular Direction)

The magnetic recording medium 10 has a squareness ratio S2 of preferably65% or more, more preferably 70% or more, still more preferably 73% ormore, further still more preferably 80% or more when the squarenessratio S2 is measured in a perpendicular direction (thickness direction)of the magnetic recording medium 10. When the squareness ratio S2 is 65%or more, perpendicular orientation of magnetic powder is sufficientlyhigh. Therefore, better SNR can be obtained. Therefore, betterelectromagnetic conversion characteristics can be obtained. Furthermore,the shape of a servo signal is improved, and it is easier to control adrive side.

Here, the perpendicular orientation of the magnetic recording medium maymean that the squareness ratio S2 of the magnetic recording medium iswithin the numerical range described above (for example, 65% or more).

The squareness ratio S2 in the perpendicular direction is determined asfollows. First, three magnetic recording media 10 are overlapped andbonded with a double-sided tape, and then punched with a φ6.39 mm punchto manufacture a measurement sample. At this time, marking is performedwith an arbitrary ink having no magnetism such that the longitudinaldirection (traveling direction) of the magnetic recording medium 10 berecognized. Then, using a VSM, an M-H loop of the measurement sample(the entire magnetic recording medium 10) corresponding to theperpendicular direction (thickness direction) of the magnetic recordingmedium 10 is measured. Next, the coating film (the underlayer 12, themagnetic layer 13, the back layer 14, and the like) is wiped off usingacetone, ethanol, and the like, leaving only the base layer 11. Then,the three base layers 11 thus obtained are overlapped and bonded with adouble-sided tape, and then punched with a φ6.39 mm punch to obtain abackground correction sample (hereinafter simply referred to as“correction sample”). Thereafter, an M-H loop of the correction sample(base layer 11) corresponding to the perpendicular direction of the baselayer 11 (perpendicular direction of the magnetic recording medium 10)is measured using a VSM.

In the measurement of the M-H loop of the measurement sample (the entiremagnetic recording medium 10) and the M-H loop of the correction sample(base layer 11), a highly sensitive vibrating sample magnetometer“VSM-P7-15 type” manufactured by Toei Industry Co., Ltd. is used. Themeasurement conditions are set to measurement mode: full loop, maximummagnetic field: 15 kOe, magnetic field step: 40 bits, time constant oflocking amp: 0.3 sec, waiting time: 1 sec, and MH average number: 20.

After the M-H loop of the measurement sample (the entire magneticrecording medium 10) and the M-H loop of the correction sample (baselayer 11) are obtained, the M-H loop of the correction sample (baselayer 11) is subtracted from the M-H loop of the measurement sample (theentire magnetic recording medium 10) to perform background correction,and an M-H loop after background correction is obtained. For thecalculation of background correction, a measurement/analysis programattached to “VSM-P7-15 type” is used.

The squareness ratio S2 (%) is calculated by putting saturationmagnetization Ms (emu) and residual magnetization Mr (emu) of theobtained M-H loop after background correction into the followingformula. Note that each of the above measurements of the M-H loops isperformed at 25° C. Furthermore, when the M-H loop is measured in theperpendicular direction of the magnetic recording medium 10,“demagnetizing field correction” is not performed. Note that for thiscalculation, the measurement/analysis program attached to “VSM-P7-15” isused.Squareness ratio S2(%)=(Mr/Ms)×100

(Squareness Ratio S1 Measured in Longitudinal Direction)

The squareness ratio S1 measured in the longitudinal direction(traveling direction) of the magnetic recording medium 10 is preferably35% or less, more preferably 30% or less, 27% or less, or 25% or less,and still more preferably 20% or less. When the squareness ratio S1 is35% or less, perpendicular orientation of magnetic powder issufficiently high. Therefore, better SNR can be obtained. Therefore,better electromagnetic conversion characteristics can be obtained.Furthermore, the shape of a servo signal is improved, and it is easierto control a drive side.

Here, the perpendicular orientation of the magnetic recording medium canmean that the squareness ratio S1 of the magnetic recording medium iswithin the numerical range described above (for example, 35% or less).The magnetic recording medium according to the present technology ispreferably perpendicularly oriented.

The squareness ratio S1 in the longitudinal direction is determined in asimilar manner to the squareness ratio S2 except that the M-H loop ismeasured in the longitudinal direction (traveling direction) of themagnetic recording medium 10 and the base layer 11.

The squareness ratios S1 and S2 are set to desired values, for example,by adjusting the intensity of a magnetic field applied to a magneticlayer forming coating material, application time of the magnetic fieldto the magnetic layer forming coating material, a dispersed state ofmagnetic powder in the magnetic layer forming coating material, and theconcentration of a solid content in the magnetic layer forming coatingmaterial. Specifically, for example, as the intensity of the magneticfield is increased, the squareness ratio S1 becomes smaller, whereas thesquareness ratio S2 becomes larger. Furthermore, as the application timeof the magnetic field is increased, the squareness ratio S1 becomessmaller, whereas the squareness ratio S2 becomes larger. Furthermore, asthe dispersed state of the magnetic powder is improved, the squarenessratio S1 becomes smaller, whereas the squareness ratio S2 becomeslarger. Furthermore, as the concentration of the solid contentdecreases, the squareness ratio S1 becomes smaller, whereas thesquareness ratio S2 becomes larger. Note that the above adjustmentmethods may be used singly or in combination of two or more thereof.

(Arithmetic Average Roughness R_(a))

The arithmetic average roughness R_(a) of the magnetic layer sidesurface (hereinafter also referred to as “magnetic surface”) of themagnetic recording medium 10 is preferably 2.5 nm or less, morepreferably 2.0 nm or less, and still more preferably 1.9 nm or less.When R_(a) is 2.5 nm or less, better SNR can be obtained.

The arithmetic average roughness R_(a) is determined as follows. First,the surface of the magnetic layer 13 is observed by AFM, and an AFMimage of 40 m×40 m is obtained. As the AFM, Dimension 3100 manufacturedby Digital Instruments and an analysis software thereof are used. Acantilever including a silicon single crystal is used (Note 1).Measurement is performed by tuning at 200 to 400 Hz as a tappingfrequency. Next, an AFM image is divided into 512×512 (=262,144)measurement points.

The height Z(i) (i: measurement point number, i=1 to 262,144) ismeasured at each measurement point. The measured heights Z(i) at themeasurement points are simply averaged (arithmetically averaged) todetermine average height (average plane) Z_(ave) (=Z(1)+Z(2)+ . . .+Z(262,144))/262,144). Subsequently, a deviation Z″(i) (=|Z(i)−Z_(ave)|)from an average center line at each measurement point is determined, andthe arithmetic average roughness R_(a)[nm](=(Z″(1)+Z″(2)+ . . .+Z″(262,144))/262,144) is calculated. In this case, as image processing,data that has been subjected to filtering processing by Flatten order 2and plane fit order 3 XY is used as data.

(Note 1) SPM probe NCH normal type Point Probe L (cantilever length)=125μm manufactured by Nano World

The arithmetic average roughness R_(a) can be adjusted by changingdrying temperature and drying time in a coating film drying stepdescribed later. The arithmetic average roughness R_(a) tends to belarger as the drying temperature is higher and as the drying time islonger.

Furthermore, the arithmetic average roughness R_(a) can be adjusted bychanging a temperature condition and a pressure condition in acalendering step described later. The arithmetic average roughness R_(a)tends to be larger as the pressure condition in the calendering step islower and as the temperature condition is lower.

(Coercive Force Hc)

The coercive force He of the magnetic recording medium 10 in alongitudinal direction thereof is preferably 2000 Oe or less, morepreferably 1900 Oe or less, and still more preferably 1800 Oe or less.When the coercive force He in the longitudinal direction is 2000 Oe orless, magnetization reacts with high sensitivity due to a magnetic fieldin a perpendicular direction from a recording head. Therefore, a goodrecording pattern can be formed.

The coercive force He measured in the longitudinal direction of themagnetic recording medium 10 is preferably 1000 Oe or more. When a lowerlimit value of the coercive force He in the longitudinal direction is1000 Oe or more, demagnetization due to a leakage magnetic flux from arecording head can be suppressed.

The above coercive force He is determined as follows. First, threemagnetic recording media 10 are overlapped and bonded with adouble-sided tape, and then punched with a φ6.39 mm punch to manufacturea measurement sample. At this time, marking is performed with anarbitrary ink having no magnetism such that the longitudinal direction(traveling direction) of the magnetic recording medium 10 be recognized.Then, an M-H loop of the measurement sample (the entire magneticrecording medium 10) corresponding to the longitudinal direction(traveling direction) of the magnetic recording medium 10 is measuredusing a vibrating sample magnetometer (VSM). Next, the coating film (theunderlayer 12, the magnetic layer 13, the back layer 14, and the like)is wiped off using acetone, ethanol, and the like, leaving only the baselayer 11. Then, the three base layers 11 thus obtained are overlappedand bonded with a double-sided tape, and then punched with a φ6.39 mmpunch to manufacture a background correction sample (hereinafter simplyreferred to as “correction sample”). Thereafter, an M-H loop of thecorrection sample (base layer 11) corresponding to the perpendiculardirection of the base layer 11 (perpendicular direction of the magneticrecording medium 10) is measured using a VSM.

In the measurement of the M-H loop of the measurement sample (the entiremagnetic recording medium 10) and the M-H loop of the correction sample(base layer 11), a highly sensitive vibrating sample magnetometer“VSM-P7-15 type” manufactured by Toei Industry Co., Ltd. is used. Themeasurement conditions are set to measurement mode: full loop, maximummagnetic field: 15 kOe, magnetic field step: 40 bits, time constant oflocking amp: 0.3 sec, waiting time: 1 sec, and MH average number: 20.

After the M-H loop of the measurement sample (the entire magneticrecording medium 10) and the M-H loop of the correction sample (baselayer 11) are obtained, the M-H loop of the correction sample (baselayer 11) is subtracted from the M-H loop of the measurement sample (theentire magnetic recording medium 10) to perform background correction,and an M-H loop after background correction is obtained. For thecalculation of background correction, a measurement/analysis programattached to “VSM-P7-15 type” is used.

The coercive force He is determined from the obtained M-H loop afterbackground correction. Note that for this calculation, themeasurement/analysis program attached to “VSM-P7-15” is used. Note thateach of the above measurements of the M-H loops is performed at 25° C.Furthermore, when the M-H loop is measured in the longitudinal directionof the magnetic recording medium 10, “demagnetizing field correction” isnot performed.

(4) Method for Manufacturing Magnetic Recording Medium

Next, a method for manufacturing the magnetic recording medium 10 havingthe above-described configuration will be described. First, by kneadingand/or dispersing nonmagnetic powder, a binder, and the like in asolvent, an underlayer forming coating material is prepared. Next, bykneading and/or dispersing magnetic powder, a binder, and the like in asolvent, a magnetic layer forming coating material is prepared. Next, bykneading and/or dispersing a binder, nonmagnetic powder, and the like ina solvent, a back layer forming coating material is prepared. For thepreparation of the magnetic layer forming coating material, theunderlayer forming coating material, and the back layer forming coatingmaterial, for example, the following solvents, dispersing devices, andkneading devices can be used.

Examples of the solvent used for preparing the above-described coatingmaterial include: a ketone-based solvent such as acetone, methyl ethylketone, methyl isobutyl ketone, or cyclohexanone; an alcohol-basedsolvent such as methanol, ethanol, or propanol; an ester-based solventsuch as methyl acetate, ethyl acetate, butyl acetate, propyl acetate,ethyl lactate, or ethylene glycol acetate; an ether-based solvent suchas diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran,or dioxane; an aromatic hydrocarbon-based solvent such as benzene,toluene, or xylene; and a halogenated hydrocarbon-based solvent such asmethylene chloride, ethylene chloride, carbon tetrachloride, chloroform,or chlorobenzene. One of these solvents may be used, or a mixture of twoor more thereof may be used.

Examples of a kneading device used for preparing the above-describedcoating materials include a kneading device such as a continuoustwin-screw kneading machine, a continuous twin-screw kneading machinecapable of performing dilution in multiple stages, a kneader, a pressurekneader, or a roll kneader, but are not particularly limited to thesedevices. Furthermore, examples of a dispersing device used for preparingthe above-described coating materials include a dispersing device suchas a roll mill, a ball mill, a horizontal sand mill, a vertical sandmill, a spike mill, a pin mill, a tower mill, a pearl mill (for example,“DCP mill” manufactured by Eirich Co., Ltd.), a homogenizer, or anultrasonic wave dispersing machine, but are not particularly limited tothese devices.

Next, the underlayer forming coating material is applied to one mainsurface of the base layer 11 and dried to form the underlayer 12.Subsequently, by applying the magnetic layer forming coating materialonto the underlayer 12 and drying the magnetic layer forming coatingmaterial, the magnetic layer 13 is formed on the underlayer 12. Notethat during drying, magnetic powder is subjected to magnetic fieldorientation in a thickness direction of the base layer 11 by, forexample, a solenoid coil. Furthermore, during drying, the magneticpowder may be subjected to magnetic field orientation in a longitudinaldirection (traveling direction) of the base layer 11 by, for example, asolenoid coil, and then may be subjected to magnetic field orientationin a thickness direction of the base layer 11. By such a magnetic fieldorientation treatment, the perpendicular orientation degree (that is,squareness ratio S1) of the magnetic powder can be improved. After themagnetic layer 13 is formed, by applying the back layer forming coatingmaterial to the other main surface of the base layer 11 and drying theback layer forming coating material, the back layer 14 is formed. As aresult, the magnetic recording medium 10 is obtained.

The squareness ratios S1 and S2 can be set to desired values, forexample, by adjusting the intensity of a magnetic field applied to acoating film of the magnetic layer forming coating material, adjustingthe concentration of a solid content in the magnetic layer formingcoating material, or adjusting drying conditions (for example, dryingtemperature and drying time) of a coating film of the magnetic layerforming coating material. The intensity of a magnetic field applied tothe coating film is preferably 2 to 3 times the coercive force of themagnetic powder. In order to further increase the squareness ratio S1(that is, to further reduce the squareness ratio S2), it is preferableto improve the dispersion state of the magnetic powder in the magneticlayer forming coating material. Furthermore, in order to furtherincrease the squareness ratio S1, it is also effective to magnetize themagnetic powder before the magnetic layer forming coating material isput into an orientation device for magnetic field orientation of themagnetic powder. Note that the above methods for adjusting thesquareness ratios S1 and S2 may be used singly or in combination of twoor more thereof.

Thereafter, the obtained magnetic recording medium 10 is calendered tosmooth the surface of the magnetic layer 13. Next, the magneticrecording medium 10 that has been calendered is wound into a roll shape.Thereafter, the magnetic recording medium 10 is heated in this state,and the large number of protrusions 14A on the surface of the back layer14 are thereby transferred onto the surface of the magnetic layer 13. Asa result, pores (a large number of holes 13A) are formed on the surfaceof the magnetic layer 13.

The temperature of the heat treatment is preferably 55° C. or higher and75° C. or lower. By adopting a temperature within this numerical rangeas the temperature of the heat treatment, the shape of the protrusion istransferred onto the magnetic layer 13 satisfactorily. In a case wherethe temperature of the heat treatment is too low (for example, less than55° C.), the shape of the protrusion is not be sufficiently transferredin some cases. In a case where the temperature of the heat treatment istoo high (for example, higher than 75° C.), the amount of pores may beexcessively increased, and the lubricant on the surface of the magneticlayer 13 may be excessive. Here, the temperature of the heat treatmentis the temperature of an atmosphere holding the magnetic recordingmedium 10.

The time for the heat treatment is preferably 15 hours or more and 40hours or less. By setting the time for the heat treatment within thisnumerical range, the shape of the protrusion is transferred onto themagnetic layer 13 satisfactorily. In a case where the time for the heattreatment is too short (for example, less than 15 hours), the shape ofthe protrusion is not be sufficiently transferred in some cases. Inorder to suppress a decrease in productivity, the time for the heattreatment is desirably set to 40 hours or less, for example.

Finally, the magnetic recording medium 10 is cut into a predeterminedwidth (for example, a width of ½ inches). The target magnetic recordingmedium 10 is thereby obtained. A servo pattern is recorded on themagnetic recording medium 10. A servo pattern may be recorded, forexample, by a servo writer known in the present technical field.

In the above manufacturing method, the large number of protrusions 14Aformed on the surface of the back layer 14 are transferred onto thesurface of the magnetic layer 13, and pores are thereby formed on thesurface of the magnetic layer 13. However, the method for forming thepores is not limited thereto. For example, pores may be formed on thesurface of the magnetic layer 13 by adjusting the type of a solventincluded in the magnetic layer forming coating material and/or adjustingdrying conditions of the magnetic layer forming coating material.Furthermore, for example, in the process of drying the solvent of themagnetic layer forming coating material, pores can be formed by anuneven distribution of the solid and the solvent included in themagnetic layer forming coating material. Furthermore, in the process ofapplying the magnetic layer forming coating material, the solventincluded in the magnetic layer forming coating material can also beabsorbed by the underlayer 12 through the pores of the underlayer 12formed when the lower layer is applied and dried. In the drying stepafter the application, the solvent moves from the underlayer 12 throughthe magnetic layer 13, and pores connecting the magnetic layer 13 to theunderlayer 12 can be thereby formed.

(5) Recording/Reproducing Device

[Configuration of Recording/Reproducing Device]

Next, an example of the configuration of the recording/reproducingdevice 30 for performing recording and reproduction for the magneticrecording medium 10 having the configuration described above will bedescribed with reference to FIG. 8 .

The recording/reproducing device 30 can adjust a tension applied to themagnetic recording medium 10 in a longitudinal direction thereof.Furthermore, the recording/reproducing device 30 can load the magneticrecording medium cartridge 10A thereon. Here, a case where therecording/reproducing device 30 can load one magnetic recording mediumcartridge 10A thereon will be described in order to facilitate thedescription. However, the recording/reproducing device 30 can load aplurality of the magnetic recording medium cartridges 10A thereon.

The recording/reproducing device 30 is connected to informationprocessing devices such as a server 41 and a personal computer(hereinafter referred to as “PC”) 42 through a network 43, and datasupplied from these information processing devices can be recorded inthe magnetic recording medium cartridge 10A. The shortest recordingwavelength of the recording/reproducing device 30 is preferably 100 nmor less, more preferably 75 nm or less, still more preferably 60 nm orless, and particularly preferably 50 nm or less.

As illustrated in FIG. 8 , the recording/reproducing device 30 includesa spindle 31, a reel 32 on the recording/reproducing device side, aspindle driving device 33, a reel driving device 34, a plurality ofguide rollers 35, a head unit 36, a communication interface(hereinafter, I/F) 37, and a control device 38.

The spindle 31 can mount the magnetic recording medium cartridge 10Athereon. The magnetic recording medium cartridge 10A conforms to thelinear tape open (LTO) standard, and rotatably houses a single reel 10Caround which the magnetic recording medium 10 is wound in a cartridgecase 10B. AV-shaped servo pattern is recorded in advance as a servosignal on the magnetic recording medium 10. The reel 32 can fix a tip ofthe magnetic recording medium 10 pulled out from the magnetic recordingmedium cartridge 10A.

The spindle driving device 33 is a device that rotationally drives thespindle 31. The reel driving device 34 is a device that rotationallydrives the reel 32. When data is recorded or reproduced on the magneticrecording medium 10, the spindle driving device 33 and the reel drivingdevice 34 rotationally drive the spindle 31 and the reel 32 to cause themagnetic recording medium 10 to travel. The guide roller 35 is a rollerfor guiding travel of the magnetic recording medium 10.

The head unit 36 includes a plurality of recording heads for recording adata signal on the magnetic recording medium 10, a plurality ofreproducing heads for reproducing a data signal recorded on the magneticrecording medium 10, and a plurality of servo heads for reproducing aservo signal recorded on the magnetic recording medium 10. For example,a ring type head can be used as the recording head, but the type of therecording head is not limited thereto.

The communication I/F 37 is for communicating with an informationprocessing device such as the server 41 or the PC 42, and is connectedto the network 43.

The control device 38 controls the entire recording/reproducing device30. For example, the control device 38 causes the head unit 36 to recorda data signal supplied from an information processing device such as theserver 41 or the PC 42 on the magnetic recording medium 10 in responseto a request from the information processing device. Furthermore, thecontrol device 38 causes the head unit 36 to reproduce a data signalrecorded on the magnetic recording medium 10 in response to a requestfrom an information processing device such as the server 41 or the PC 42and supplies the data signal to the information processing device.

The control device 38 controls the entire recording/reproducing device30. For example, the control device 38 causes the head unit 36 to recorda data signal supplied from an information processing device such as theserver 41 or the PC 42 on the magnetic recording medium 10 in responseto a request from the information processing device. Furthermore, thecontrol device 38 causes the head unit 36 to reproduce a data signalrecorded on the magnetic recording medium 10 in response to a requestfrom an information processing device such as the server 41 or the PC 42and supplies the data signal to the information processing device.

Furthermore, the control device 38 controls a rotational drive torque ofat least one of the reel driving device 34 or the spindle driving device33 on the basis of information stored in a cartridge memory 211 includedin the cartridge 10A including the magnetic recording medium 10,described later, and thereby can adjust a tension applied to themagnetic recording medium 10 in a longitudinal direction thereof

[Operation of Recording/Reproducing Device]

Next, operation of the recording/reproducing device 30 having theconfiguration described above will be described.

First, the magnetic recording medium cartridge 10A is mounted on therecording/reproducing device 30. A tip of the magnetic recording medium10 is pulled out, transferred to the reel 32 via the plurality of guiderollers 35 and the head unit 36, and attached to the reel 32.

Next, when an operation unit (not illustrated) is operated, the spindledriving device 33 and the reel driving device 34 are driven by controlof the control device 38. As a result, the spindle 31 and the reel 32are rotated in the same direction such that the magnetic recordingmedium 10 is wound around the reel 32 and the magnetic recording medium10 travels from the reel 10C toward the reel 32 in the head unit 36.Therefore, information is recorded on the magnetic recording medium 10,or information recorded on the magnetic recording medium 10 isreproduced.

Furthermore, in a case where the magnetic recording medium 10 is rewoundonto the reel 10C, the spindle 31 and the reel 32 are rotationallydriven in the opposite direction to the direction described above, andthe magnetic recording medium 10 thereby travels from the reel 32 to thereel 10C. Also during the rewinding, the head unit 36 recordsinformation on the magnetic recording medium 10 or reproducesinformation recorded on the magnetic recording medium 10.

(6) Cartridge

[Configuration of Cartridge]

The present technology also provides a magnetic recording cartridge(also referred to as a tape cartridge) including the magnetic recordingmedium according to the present technology. In the magnetic recordingcartridge, the magnetic recording medium may be wound around a reel, forexample. For example, the magnetic recording cartridge may include: acommunication unit that communicates with a recording/reproducingdevice; a storage unit; and a control unit that stores informationreceived from the recording/reproducing device through the communicationunit in the storage unit, reads the information from the storage unitaccording to a request from the recording/reproducing device, andtransmits the information to the recording/reproducing device throughthe communication unit. The information can include adjustmentinformation for adjusting a tension applied to the magnetic recordingmedium in a longitudinal direction thereof. The adjustment informationcan include, for example, dimensional information in the width directionat a plurality of positions in the longitudinal direction of themagnetic recording medium. The dimensional information in the widthdirection may be dimensional information at the time of manufacturing amagnetic recording medium (initial stage after manufacture) describedbelow in [Configuration of cartridge memory] and/or dimensionalinformation acquired in the dimensional information acquiring stepdescribed in “(7) Data processing method” below.

An example of the configuration of the cartridge 10A including themagnetic recording medium 10 having the above-described configurationwill be described with reference to FIG. 12 .

FIG. 12 is an exploded perspective view illustrating an example of aconfiguration of the cartridge 10A. The cartridge 10A is a magneticrecording medium cartridge conforming to the linear tape-open (LTO)standard, and includes: in the cartridge case 10B including a lowershell 212A and an upper shell 212B, a reel 10C around which a magnetictape (tape-shaped magnetic recording medium) 10 is wound; a reel lock214 and a reel spring 215 for locking rotation of the reel 10C; a spider216 for releasing a locked state of the reel 10C; a slide door 217 thatopens and closes a tape outlet 212C formed in the cartridge case 10B soas to straddle the lower shell 212A and the upper shell 212B; a doorspring 218 that urges the slide door 217 to a closed position of thetape outlet 212C; a write protect 219 for preventing erroneous erasure;and a cartridge memory 211. The reel 10C has a substantially disk shapewith an opening at the center, and incudes a reel hub 213A and a flange213B including a hard material such as plastic. A leader pin 220 isdisposed at one end of the magnetic tape 10.

The cartridge memory 211 is disposed near one corner of the cartridge10A. The cartridge memory 211 faces a reader/writer (not illustrated) ofthe recording/reproducing device 30 in a state where the cartridge 10Ais loaded on the recording/reproducing device 30. The cartridge memory211 communicates with the recording/reproducing device 30, specifically,with a reader/writer (not illustrated) according to a wirelesscommunication standard conforming to the LTO standard.

[Configuration of Cartridge Memory]

An example of the configuration of the cartridge memory 211 will bedescribed with reference to FIG. 13 .

FIG. 13 is a block diagram illustrating an example of a configuration ofthe cartridge memory 211. The cartridge memory 211 includes: an antennacoil (communication unit) 331 that communicates with a reader/writer(not illustrated) according to a prescribed communication standard; arectification/power supply circuit 332 that generates power using aninduced electromotive force from a radio wave received by an antennacoil 331 and performs rectification to generate a power supply; a clockcircuit 333 that generates a clock using an induced electromotive forcesimilarly from the radio wave received by the antenna coil 331; adetection/modulation circuit 334 that performs detection of the radiowave received by the antenna coil 331 and modulation of a signaltransmitted by the antenna coil 331; a controller (control unit) 335including a logic circuit and the like for determining a command anddata from a digital signal extracted from the detection/modulationcircuit 334 and processing the command and data; and a memory (storageunit) 336 that stores information. Furthermore, the cartridge memory 211includes a capacitor 337 connected in parallel to the antenna coil 331,and the antenna coil 331 and the capacitor 337 constitute a resonantcircuit.

The memory 336 stores information and the like related to the cartridge10A. The memory 336 is a non-volatile memory (NVM). The memory 336preferably has a storage capacity of about 32 KB or more. For example,in a case where the cartridge 10A conforms to the LTO-9 standard or theLTO-10 standard, the memory 336 has a storage capacity of about 32 KB.

The memory 336 has a first storage area 336A and a second storage area336B. The first storage area 336A corresponds to a storage area of acartridge memory conforming to an LTO standard prior to LTO 8(hereinafter referred to as “conventional cartridge memory”) and is anarea for storing information conforming to an LTO standard prior to LTO8. The information conforming to an LTO standard prior to LTO 8 is, forexample, manufacturing information (for example, a unique number of thecartridge 10) or a usage history (for example, the number of times oftape withdrawal (thread count)).

The second storage area 336B corresponds to an extended storage area fora storage area of the conventional cartridge memory. The second storagearea 336B is an area for storing additional information. Here, theadditional information means information related to the cartridge 10A,not prescribed by an LTO standard prior to LTO 8. Examples of theadditional information include tension adjustment information,management ledger data, Index information, and thumbnail information ofa moving image stored in the magnetic tape 10, but are not limited tothe data. The tension adjustment information includes, as initialinformation, dimensional information in the width direction at the timeof manufacturing the magnetic recording medium 10 (initial stage aftermanufacture). Note that the dimensional information in the widthdirection at the time of manufacturing the magnetic recording medium 10is a constant value (specified value) at an arbitrary position in thelongitudinal direction.

The memory 336 may have a plurality of banks. In this case, some of theplurality of banks may constitute the first storage area 336A, and theremaining banks may constitute the second storage area 336B.Specifically, for example, in a case where the cartridge 10A conforms tothe LTO-9 standard or the LTO-10 standard, the memory 336 may have twobanks each having a storage capacity of about 16 KB. One of the twobanks may constitute the first storage area 336A, and the other bank mayconstitute the second storage area 336B.

The antenna coil 331 induces an induced voltage by electromagneticinduction. The controller 335 communicates with therecording/reproducing device 30 according to a prescribed communicationstandard through the antenna coil 331. Specifically, for example, mutualauthentication, transmission and reception of commands, and exchange ofdata are performed.

The controller 335 stores information received from therecording/reproducing device 30 through the antenna coil 331 in thememory 336. The controller 335 reads out information from the memory 336in response to a request from the recording/reproducing device 30, andtransmits the information to the recording/reproducing device 30 throughthe antenna coil 331.

(7) Data Processing Method

The present technology also provides a data processing method using themagnetic recording medium according to the present technology. The dataprocessing method may be, for example, a recording method for recordingdata on the magnetic recording medium according to the presenttechnology, a reproduction method for reproducing data recorded on themagnetic recording medium according to the present technology, or amethod for recording data on the magnetic recording medium according tothe present technology and reproducing data recorded on the magneticrecording medium.

The data processing method includes: a dimensional information acquiringstep of acquiring dimensional information in a width direction at aplurality of positions in a longitudinal direction of the tape-shapedmagnetic recording medium according to the present technology while themagnetic recording medium is caused to travel with a tension applied ina longitudinal direction thereof; and a data processing step ofrecording data on the magnetic recording medium while the magneticrecording medium is caused to travel with a tension applied in alongitudinal direction thereof and/or reproducing the data recorded onthe magnetic recording medium. In the data processing step, a tensionapplied to the magnetic recording medium in a longitudinal directionthereof is adjusted on the basis of the dimensional information.

The data processing method according to the present technology recordsand/or reproduces data while adjusting a tension as described above. Themagnetic recording medium according to the present technology used inthe method is suitable for use in a data processing method forperforming recording and reproduction while adjusting the width of themagnetic recording medium by adjusting a tension of the magneticrecording medium in a longitudinal direction thereof. Therefore, theadvantage of the magnetic recording medium according to the presenttechnology is effectively exhibited by the data processing methodaccording to the present technology.

According to a preferred embodiment of the present technology, in thedata processing step, a tension applied to the magnetic recording mediumin a longitudinal direction thereof may be adjusted on the basis of thedimensional information and initial dimensional information acquired inadvance before the dimensional information acquiring step is performed.

The initial dimensional information may be, for example, dimensionalinformation of the magnetic recording medium in a width directionthereof at any time before the dimension acquiring step is performed.For example, it is assumed that a magnetic recording cartridge includingthe magnetic recording medium is sold, and then the data processingmethod according to the present technology is performed using themagnetic recording medium included in the magnetic recording cartridge.In this case, the initial dimensional information may be acquired at anytime before the magnetic recording cartridge is sold, or may be acquiredat any time from the time when the magnetic recording cartridge is soldto the time when the data processing method according to the presenttechnology is performed. In the former case, the initial dimensionalinformation can correspond to, for example, dimensional information inthe width direction at the time of manufacturing the magnetic recordingmedium 10 (initial stage after manufacture), described in the above “(6)Cartridge”. In the latter case, the initial dimensional information maybe acquired when data is recorded on the magnetic recording cartridgefor the first time, for example. More specifically, the initialdimensional information may be acquired in a case where the magneticrecording cartridge is inserted into a drive in order to perform datarecording on the magnetic recording cartridge for the first time.

Preferably, the initial dimensional information is dimensionalinformation of the magnetic recording medium in a width directionthereof, acquired at the plurality of positions in the longitudinaldirection from which the dimensional information has been acquired inthe dimensional information acquiring step. That is, the position in thelongitudinal direction from which the dimensional information has beenacquired is preferably the same as the position in the longitudinaldirection from which the initial dimensional information has beenacquired. As a result, it is possible to more easily calculate a tensionto be applied to the magnetic recording medium in a longitudinaldirection thereof in the data processing step.

The acquisition of the initial dimensional information may be performedby the same method as the acquisition of the dimensional information inthe dimensional information acquiring step or may be performed by adifferent method therefrom, but is preferably performed by the samemethod.

According to one preferred embodiment of the present technology, in thedata processing step, a tension applied to the magnetic recording mediumin a longitudinal direction thereof can be adjusted such that thedimensional information corresponds to the initial dimensionalinformation. For example, the tension may be adjusted such that thedimensions at each of the plurality of positions recorded as thedimensional information approach the dimensions at each of the pluralityof positions recorded as the initial dimensional information. Morepreferably, the tension may be adjusted such that the dimensions at eachof the plurality of positions recorded as the initial dimensionalinformation match the dimensions at each of the plurality of positionsrecorded as the dimensional information.

According to one preferred embodiment of the present technology, thedata processing method may further include an information acquiring stepof acquiring at least one of environmental information around themagnetic recording medium or traveling condition information. In thedata processing step, the tension applied to the magnetic recordingmedium in the longitudinal direction can be adjusted on the basis of thedimensional information and at least one of the environmentalinformation or the traveling condition information. In the adjustment ofthe tension, in consideration of at least one of the environmentalinformation or the traveling condition information in addition to thedimensional information, a more appropriate tension can be applied tothe magnetic recording medium.

The environmental information preferably includes one or both oftemperature information and humidity information around the magneticrecording medium. The traveling condition information preferablyincludes tension information when the magnetic recording medium iswound. The temperature information and the humidity information canaffect the dimensions of the magnetic recording medium, and the tensioninformation when the magnetic recording medium is wound can affect widthcontrollability of the magnetic recording medium. Therefore, use of theinformation makes it possible to apply a more appropriate tension to themagnetic recording medium.

An example of a procedure performed for recording data on a magneticrecording medium using the method according to the present technologywill be described with reference to the flowchart of FIG. 14 . In thisexample, it is assumed that data is recorded on the magnetic recordingmedium 10 using the recording/reproducing device 30 illustrated in FIG.8 . Furthermore, it is assumed that the recording/reproducing device 30or the cartridge 10A includes a thermometer/hygrometer (notillustrated), and temperature information and/or humidity informationaround the magnetic recording medium 10 (for example, an environment inwhich the recording/reproducing device 30 is placed) is sent to thecontrol device 38 from the thermometer/hygrometer.

In step S101, the cartridge 10A (tape cartridge) including the magneticrecording medium 10 (magnetic tape) is set in the recording/reproducingdevice 30 (drive). In response to the cartridge 10A being set, thecontrol device 38 determines whether or not initial dimensionalinformation is stored in the cartridge memory 211 (particularly memory336) of the cartridge 10A. In response to the initial dimensionalinformation not being stored, the control device 38 causes the processto proceed to step S102. In a case where the initial dimensionalinformation is stored, step S104 may be performed without performingsteps S102 and 103.

In step S102, the control device 38 drives the reel driving device 34and the spindle driving device 33, and the spindle 31 and the reel 32are rotated in the same direction such that the magnetic recordingmedium 10 travels from the reel 10C toward the reel 32. As a result, themagnetic recording medium 10 travels from the reel 10C toward the reel32. After the travel is completed, the control device 38 drives the reeldriving device 34 and the spindle driving device 33, and the spindle 31and the reel 32 are rotated in the same direction such that the magneticrecording medium 10 travels from the reel 32 toward the reel 10C. As aresult, the magnetic recording medium 10 travels from the reel 32 towardthe reel 10C. In the course of traveling in this way, the control device38 acquires dimensional information of the magnetic recording medium 10in a width direction thereof at each of a plurality of positions of themagnetic recording medium 10 in a longitudinal direction thereof. Inorder to acquire the dimensional information, for example, a servosignal acquired by the head unit 36 may be used. For example, by using aservo signal recorded in advance on the magnetic recording medium 10,dimensional information in the width direction (for example, servobandwidth) can be acquired. The control device 38 stores the acquireddimensional information in the cartridge memory 211 (particularly thememory 336). The dimensional information is recorded in the cartridgememory 211 in association with the position where the dimensionalinformation has been acquired.

In step S102, a tension applied to the magnetic recording medium 10 maybe constant, for example, 0.1 N to 2 N, particularly 0.2 N to 1 N, moreparticularly 0.3 N to 0.8 N, and still more particularly 0.4 N to 0.6 N.

In step S102, the plurality of positions from which the dimensionalinformation in the width direction is acquired may be, for example,division positions when the total length of the magnetic recordingmedium 10, is equally divided into, for example, 10 to 500, particularly20 to 200, more particularly 50 to 150, still more particularly 80 to120.

In step S103, the control device 38 can acquire environmentalinformation. For example, the control device 38 acquires temperatureinformation and/or humidity information from the thermometer/hygrometer,and stores the acquired temperature information and/or humidityinformation in the cartridge memory 211. Furthermore, in step S103, thecontrol device 38 may acquire traveling condition information inaddition to the environmental information or instead of theenvironmental information. The traveling condition information can be,for example, the tension applied in step S102. Step S103 does not needto be performed, but step S103 makes it possible to apply a moreappropriate tension to the magnetic recording medium.

In step S104, the control device 38 receives a data recording startrequest. The data recording start request can be transmitted to thecontrol device 38 by operation of the recording/reproducing device 30 bya user of the magnetic recording medium 10, for example. When receivingthe data recording start request, the control device 38 advances theprocess to step S105.

In step S105, the control device 38 causes the head unit 36 to record adata signal supplied from an information processing device such as theserver 41 or the PC 42 on the magnetic recording medium 10 in responseto a request from the information processing device. For example, in therecording, the magnetic recording medium 10 is caused to travel from thereel 10C toward the reel 32.

As described above, in steps S101 to S105, initial width information isrecorded in a cartridge memory for a magnetic recording cartridge inwhich the initial width information is not recorded in the cartridgememory, and then data is recorded in the magnetic recording medium.

The above step S105 is performed, and the magnetic recording medium 10is stored for a short time or for a long time. Thereafter, data isrecorded and/or reproduced. The recording and/or reproduction are/isperformed according to the data processing method according to thepresent technology. That is, at least the dimensional informationacquiring step and the data processing step are performed.

(8) Effect

The magnetic recording medium 10 according to the present technologyincludes: a magnetic layer; an underlayer; a base layer; and a backlayer, in which the underlayer has a thickness of 0.5 μm or more and 0.9μm or less, the magnetic recording medium has an average thickness t_(T)of 5.6 μm or less, the magnetic recording medium includes a lubricant,the magnetic recording medium has pores, and the pores have an averagediameter of 6 nm or more and 11 nm or less when the diameters of thepores are measured in a state where the lubricant has been removed fromthe magnetic recording medium and the magnetic recording medium has beendried, and the Young's modulus in a longitudinal direction is 7.90 GPaor less. As a result, the magnetic recording medium 10 has excellenttraveling stability in spite of having a thin total thickness and a thinthickness of an underlayer, and is suitable for use in arecording/reproducing device for suppressing a dimensional change of themagnetic recording medium 10 in a width direction thereof by adjusting atension applied to the magnetic recording medium 10 in a longitudinaldirection thereof.

In the data processing method according to the present technology, datais recorded and/or reproduced while the tension is adjusted as describedabove, and the magnetic recording medium according to the presenttechnology used in the method is suitable for use in a data processingmethod for performing recording and reproduction while adjusting thewidth of the magnetic recording medium by adjusting a tension of themagnetic recording medium in a longitudinal direction thereof.Therefore, the advantage of the magnetic recording medium according tothe present technology is effectively exhibited by the data processingmethod according to the present technology.

(9) Modification Modification 1

The magnetic recording medium 10 may further include a barrier layer 15disposed on at least one surface of the base layer 11, as illustrated inFIG. 9 . The barrier layer 15 is a layer for suppressing a dimensionalchange of the base layer 11 according to an environment. Examples of acause of the dimensional change include the hygroscopic property of thebase layer 11. However, by disposing the barrier layer 15, a penetrationrate of moisture into the base layer 11 can be reduced. The barrierlayer 15 includes a metal or a metal oxide. As the metal, for example,at least one of Al, Cu, Co, Mg, S1, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge,Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, Au, or Ta can be used. As the metaloxide, for example, at least one of Al₂O₃, CuO, CoO, SiO₂, Cr₂O₃, TiO₂,Ta₂O₅, or ZrO₂ can be used, and any one of oxides of the metalsdescribed above can also be used. Furthermore, diamond-like carbon(DLC), diamond, and the like can also be used.

The average thickness of the barrier layer 15 is preferably 20 nm ormore and 1000 nm or less, and more preferably 50 nm or more and 1000 nmor less. The average thickness of the barrier layer 15 is determined ina similar manner to the average thickness t_(m) of the magnetic layer13. However, a magnification of a TEM image is appropriately adjustedaccording to the thickness of the barrier layer 15.

Modification 2

The magnetic recording medium 10 may be incorporated in a librarydevice. That is, the present technology also provides a library deviceincluding at least one magnetic recording medium 10. The library devicecan adjust a tension applied to the magnetic recording medium 10 in alongitudinal direction thereof, and may include a plurality of therecording/reproducing devices 30 described above.

3. EXAMPLES

Hereinafter, the present technology will be described specifically withExamples, but the present technology is not limited only to theseExamples.

In the following Examples and Comparative Examples, the averagethickness t_(T) of a magnetic tape, the surface roughness of a magneticlayer (arithmetic average roughness of a magnetic layer side surface)R_(a), the squareness ratio S2, the average thickness t_(m) of themagnetic layer, the average diameter of pores, SNR, the frictioncoefficient ratio (μ_(B)/μ_(A)), and the friction coefficient ratio(μ_(C(1000))/μ_(C(5))) are values determined by the measurement methoddescribed in “2. Embodiment of the present technology (example ofapplication type magnetic recording medium)”.

(1) Manufacture of Magnetic Tape

As described below, magnetic tapes of Examples 1 to 21 and ComparativeExamples 1 to 7 were manufactured. Table 1 below illustrates the squareratios S2 and S1 of each of these magnetic tapes, the average diameterof pores, average thickness t_(m) of a magnetic layer, the averagethickness of an underlayer, the average thickness of a base layer, theaverage thickness of a back layer, the average thickness t_(T) of eachof the magnetic tapes, coating film thickness/base thickness, Young'smodulus, surface roughness (magnetic surface roughness) R_(a) of amagnetic layer, the type of magnetic powder, the shape thereof, theaspect ratio thereof, and the particle volume thereof.

Example 1

(Step of Preparing Magnetic Layer Forming Coating Material)

A magnetic layer forming coating material was prepared as follows.First, a first composition having the following formulation was kneadedwith an extruder. Next, the kneaded first composition and a secondcomposition having the following formulation were added to a stirringtank equipped with a disper, and were premixed. Subsequently, themixture was further subjected to sand mill mixing, and was subjected toa filter treatment to prepare a magnetic layer forming coating material.

(First Composition)

Powder of barium ferrite (BaFe₁₂O₁₉) particles (hexagonal plate shape,average particle volume 1950 nm³): 100 parts by mass

Cyclohexanone solution of vinyl chloride-based resin: 65 parts by mass

(The composition of the solution is 30% by mass of the resin and 70% bymass of cyclohexanone. Details of the vinyl chloride-based resin were asfollows: (Degree of polymerization: 300, Mn=10000, OSO₃K=0.07 mmol/g andsecondary OH=0.3 mmol/g were contained as polar groups.)

Aluminum oxide powder: 5 parts by mass

(α-Al2O3, average particle diameter: 0.2 μm)

Carbon black: 2 parts by mass

(Manufactured by Tokai Carbon Co., Ltd., trade name: Seast TA)

(Second Composition)

Cyclohexanone solution of vinyl chloride-based resin: 3 parts by mass

(The composition of the solution is 30% by mass of the resin and 70% bymass of cyclohexanone.

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 121.3 parts by mass

Toluene: 121.3 parts by mass

Cyclohexanone: 60.7 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Tosoh Corporation) as a curing agent and 2 parts by massof stearic acid as a lubricant were added to the magnetic layer formingcoating material prepared as described above.

(Step of Preparing Underlayer Forming Coating Material)

An underlayer forming coating material was prepared as follows. First, athird composition having the following formulation was kneaded with anextruder. Next, the kneaded third composition and a fourth compositionhaving the following formulation were added to a stirring tank equippedwith a disper, and were premixed. Subsequently, the mixture was furthersubjected to sand mill mixing, and was subjected to a filter treatmentto prepare an underlayer forming coating material.

(Third composition)

Acicular Iron Oxide Powder: 100 Parts by Mass

(α-Fe₂O₃, average long axis length 0.15 μm)

Cyclohexanone solution of vinyl chloride-based resin: 55.6 parts by mass

(The composition of the solution is 30% by mass of the resin and 70% bymass of cyclohexanone.

Carbon black: 10 parts by mass

(Average particle diameter 20 nm)

(Fourth Composition)

Polyurethane-based resin UR8200 (manufactured by Toyobo Co., Ltd.): 20.0parts by mass

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 108.2 parts by mass

Toluene: 108.2 parts by mass

Cyclohexanone: 18.5 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Tosoh Corporation) as a curing agent and 2 parts by massof stearic acid as a lubricant were added to the underlayer formingcoating material prepared as described above.

(Step of preparing back layer forming coating material) Aback layerforming coating material was prepared as follows. The following rawmaterials were mixed in a stirring tank equipped with a disper, and weresubjected to filter treatment to prepare a back layer forming coatingmaterial. Carbon black powder having a small particle diameter (averageparticle diameter (D50) 20 nm): 90 parts by mass

Carbon black powder having a large particle diameter (average particlediameter (D50) 270 nm): 10 parts by mass

Polyester polyurethane: 100 parts by mass

(trade name: N-2304, manufactured by Tosoh Corporation)

Methyl ethyl ketone: 500 parts by mass

Toluene: 400 parts by mass

Cyclohexanone: 100 parts by mass

(Application Step)

Using the magnetic layer forming coating material and the underlayerforming coating material prepared as described above, an underlayer anda magnetic layer were formed on one main surface of a long poleethylenenaphthalate film (hereinafter referred to as “PEN film”) having anaverage thickness of 4.00 μm as a nonmagnetic support (base layer) suchthat the average thickness of the underlayer was 0.60 μm and the averagethickness of the magnetic layer was 0.08 μm after drying and calenderingas follows. First, the underlayer forming coating material was appliedonto one main surface of the PEN film and dried to form an underlayer.Next, the magnetic layer forming coating material was applied on theunderlayer and dried to form a magnetic layer. Note that the magneticpowder was subjected to magnetic field orientation in a thicknessdirection of the film by a solenoid coil when the magnetic layer formingcoating material was dried. Furthermore, drying conditions (dryingtemperature and drying time) of the magnetic layer forming coatingmaterial were adjusted, and the squareness ratio S1 of the magnetic tapein the thickness direction (perpendicular direction) and the squarenessratio S2 thereof in the longitudinal direction were set to the valuesillustrated in Table 1. Subsequently, the back layer forming coatingmaterial was applied onto the other main surface of the PEN film anddried to form a back layer having an average thickness of 0.30 μm. As aresult, a magnetic tape was obtained. The magnetic tape had a magneticsurface roughness R_(a) (arithmetic average roughness) of 1.80 μm.

(Calendering Step and Transfer Step)

Subsequently, a calendering treatment was performed under predeterminedtemperature condition and pressure condition to smooth the surface ofthe magnetic layer. Next, the magnetic tape thus obtained was wound intoa roll shape, and then the magnetic tape was heated at 60° C. for 10hours in this state. Then, the magnetic tape was rewound in a roll shapesuch that an end located on an inner circumferential side was located onan outer circumferential side oppositely, and then the magnetic tape washeated again at 60° C. for 10 hours in this state. As a result, a largenumber of protrusions on the surface of the back layer were transferredonto the surface of the magnetic layer to form a large number of holeson the surface of the magnetic layer.

(Cutting Step)

The magnetic tape obtained as described above was cut into a width of ½inches (12.65 mm). As a result, the target long magnetic tape (averagethickness 5.0 μm) was obtained.

Example 2

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 30% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, and the thickness of the underlayerwas changed to set the average thickness t_(T) of the magnetic recordingmedium to 5.2 μm.

Example 3

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 27% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 71%

Example 4

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 29% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 70%, and the thicknesses of the underlayerand the back layer were changed to set the average thickness t_(T) ofthe magnetic recording medium to 5.5 km.

Example 5

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 30% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the heating temperature in the heattreatment after the calendering treatment was lowered to change theaverage diameter of pores to 6 nm, and the drying temperature in theabove coating film drying step was lowered to change the arithmeticaverage roughness R_(a) of the magnetic layer side surface to 1.70 μm.

Example 6

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 30% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, and the thickness of the underlayerwas changed to set the average thickness t_(T) of the magnetic recordingmedium to 5.3 μm.

Example 7

A magnetic tape was manufactured by the same method as in Example 6except that the thicknesses of the underlayer and the base layer werechanged to set the average thickness t_(T) of the magnetic recordingmedium to 4.7 μm.

Example 8

A magnetic tape was manufactured by the same method as in Example 6except that the magnetic powder contained in the magnetic layer waschanged from powder of barium ferrite particles to powder of ε ironoxide particles, and the thickness of the underlayer was changed to setthe average thickness t_(T) to 5.0 μm.

Example 9

A magnetic tape was manufactured by the same method as in Example 6except that the magnetic powder contained in the magnetic layer waschanged from powder of barium ferrite particles to powder of Co ironoxide particles, and the thickness of the underlayer was changed to setthe average thickness t_(T) to 5.0 μm.

Example 10

A magnetic tape was manufactured by the same method as in Example 6except that the thicknesses of the base layer and the back layer werechanged to set the average thickness t_(T) of the magnetic recordingmedium to 5.6 μm.

Example 11

A magnetic tape was manufactured by the same method as in Example 6except that the heating temperature in the heat treatment after thecalendering treatment was lowered to change the average diameter ofpores to 10 nm, and the drying temperature was raised and the dryingtime was increased in the above coating film drying step to change thearithmetic average roughness R_(a) of the magnetic layer side surface to1.90 μm.

Example 12

A magnetic tape was manufactured by the same method as in Example 6except that the heating temperature in the heat treatment after thecalendering treatment was lowered and the average diameter of pores waschanged to 6 nm. Note that in Example 12, the arithmetic averageroughness R_(a) of the magnetic layer side surface is the same value(1.80 μm) as that in Example 6 by lowering the drying temperature in theabove coating film drying step and lowering the pressure condition inthe calendering step.

Example 13

A magnetic tape was obtained by the same method as in Example 1 exceptthat the application time of the magnetic field to the magnetic layerforming coating material was adjusted to set the squareness ratio S1 ofthe magnetic tape in the longitudinal direction to 23% and to set thesquareness ratio S2 thereof in the thickness direction (perpendiculardirection) to 75%

Example 14

A magnetic tape was obtained by the same method as in Example 1 exceptthat the application time of the magnetic field to the magnetic layerforming coating material was adjusted to set the squareness ratio S1 ofthe magnetic tape in the longitudinal direction to 20% and to set thesquareness ratio S2 thereof in the thickness direction (perpendiculardirection) to 80%

Example 15

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 30% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the heating temperature in the heattreatment after the calendering treatment was lowered to change theaverage diameter of pores to 11 nm, and the drying temperature in theabove coating film drying step was set to a very high temperature andthe drying time was increased to set the arithmetic average roughnessR_(a) of the magnetic layer side surface to 1.90 μm.

Example 16

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 30% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, and the thickness of the underlayerwas changed to set the average thickness t_(T) of the magnetic recordingmedium to 4.9 μm.

Example 17

A magnetic tape was manufactured by the same method as in Example 6except that the thicknesses of the magnetic layer and the underlayerwere changed to set the average thickness t_(T) of the magneticrecording medium to 5.0 μm, and the pressure condition in the abovecalendering step was lowered to set the arithmetic average roughnessR_(a) of the magnetic layer side surface to 1.90 μm.

Example 18

A magnetic tape was manufactured by the same method as in Example 6except that the thicknesses of the magnetic layer and the underlayerwere changed to set the average thickness t_(T) of the magneticrecording medium to 4.9 μm, and the pressure condition in the abovecalendering step was lowered to set the arithmetic average roughnessR_(a) of the magnetic layer side surface to 1.90 μm.

Example 19

A magnetic tape was manufactured by the same method as in Example 6except that as the nonmagnetic support (base layer), a polyethyleneterephthalate (PET) film (hereinafter referred to as PET film) was usedinstead of the PEN film, the thicknesses of the magnetic layer, theunderlayer, and the base layer were changed to set the average thicknesst_(T) of the magnetic recording medium to 5.1 μm, and the pressurecondition in the above calendering step was lowered to set thearithmetic average roughness R_(a) of the magnetic layer side surface to1.90 μm.

Example 20

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 42% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 60%

Example 21

A magnetic tape was manufactured by the same method as in Example 1except that the thicknesses of the magnetic layer and the underlayerwere changed to set the average thickness t_(T) of the magneticrecording medium to 5.2 μm.

Comparative Example 1

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the heating temperature in the heattreatment after the calendering treatment was lowered to change theaverage diameter of pores to 5 nm, and the drying temperature in theabove coating film drying step was lowered and the drying time wasincreased to set the arithmetic average roughness R_(a) of the magneticlayer side surface to 1.60 μm.

Comparative Example 2

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the heating temperature in the heattreatment after the calendering treatment was lowered to change theaverage diameter of pores to 10 nm, the thickness of the underlayer waschanged to set the average thickness t_(T) of the magnetic recordingmedium to 5.4 μm, and the drying temperature was raised and the dryingtime was increased in the above coating film drying step to set thearithmetic average roughness R_(a) of the magnetic layer side surface to1.90 μm.

Comparative Example 3

A magnetic tape was manufactured by the same method as in Example 1except that the thickness of the underlayer was changed to set theaverage thickness t_(T) of the magnetic recording medium to 4.8 μm, andthe temperature condition and pressure condition in the abovecalendering step were raised to set the arithmetic average roughnessR_(a) of the magnetic layer side surface to 1.70 μm.

Comparative Example 4

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the heating temperature in the heattreatment after the calendering treatment was lowered to change theaverage diameter of pores to 12 nm, the thickness of the underlayer waschanged to set the average thickness t_(T) of the magnetic recordingmedium to 5.2 μm, and the drying temperature was raised and the dryingtime was increased in the above coating film drying step and thepressure condition in the calendering step was lowered to set thearithmetic average roughness R_(a) of the magnetic layer side surface to2.00 μm.

Comparative Example 5

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the thickness of the underlayer waschanged to set the average thickness t_(T) of the magnetic recordingmedium to 5.6 μm, and the pressure condition in the calendering step waslowered to set the arithmetic average roughness R_(a) of the magneticlayer side surface to 1.90 μm.

Comparative Example 6

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the thicknesses of the underlayer, thebase layer, and the back layer were changed to set the average thicknesst_(T) of the magnetic recording medium to 5.7 μm, and the pressurecondition in the calendering step was lowered to set the arithmeticaverage roughness R_(a) of the magnetic layer side surface to 1.90 μm.

Comparative Example 7

A magnetic tape was manufactured by the same method as in Example 1except that the application time of the magnetic field to the magneticlayer forming coating material was adjusted to set the squareness ratioS1 of the magnetic tape in the longitudinal direction to 31% and to setthe squareness ratio S2 thereof in the thickness direction(perpendicular direction) to 66%, the thicknesses of the magnetic layer,the underlayer, and the back layer were changed to set the averagethickness t_(T) of the magnetic recording medium to 5.7 μm, and thepressure condition in the calendering step was lowered to set thearithmetic average roughness R_(a) of the magnetic layer side surface to1.90 μm.

(2) Evaluation

For each of the magnetic tapes of Examples 1 to 21 and ComparativeExamples 1 to 7 manufactured in (1) described above, the frictioncoefficient ratios (μ_(B)/μ_(A)) and (μ_(C(1000))/μ_(C(5))) and theamount of width change were measured. These measurements were performedby the measurement method described in “2. Embodiment of the presenttechnology (example of application type magnetic recording medium)”. Themeasurement results are illustrated in Table 1 below.

Moreover, the SNR was evaluated for each of the magnetic tapes ofExamples 1 to 21 and Comparative Examples 1 to 7. The evaluation resultsare illustrated in Table 1 below. A method for evaluating SNR was asfollows.

(SNR)

First, using a ½ inch tape traveling device (manufactured by MountainEngineering II, MTS Transport) equipped with a recording/reproducinghead and a recording/reproducing amplifier, the electromagneticconversion characteristics (SNR) of each of the magnetic tapes weremeasured in an environment of 25° C. A ring head having a gap length of0.2 μm was used as the recording head, and a GMR head having ashield-to-shield distance of 0.1 μm was used as the reproducing head. Arelative speed, a recording clock frequency, and a recording track widthwere set to 6 m/s, 160 MHz, and 2.0 μm, respectively. Furthermore, theSNR was calculated on the basis of a method described in the followingdocument. The results are illustrated in Table 1 as relative values whenthe SNR of Example 1 is 0 dB.

Y Okazaki: “An Error Rate Emulation System.”, IEEE Trans. Man., 31, pp.3093-3095 (1995)

TABLE 1 Squareness ratio S2 Coating in perpendicular Squareness AverageAverage Average Average Average film direction (without ratio S1 indiameter thickness thickness of thickness thickness Average thickness/demagnetizing longitudinal of pores of magnetic underlayer of base ofback thickness base field correction) [%] direction [%] [nm] layer (μm)(μm) layer (μm) layer (μm) t_(T) (μm) thickness Example 1  65 35 8 0.080.6 4.0 0.3 5.0 0.25 Example 2  66 30 8 0.08 0.8 4.0 0.3 5.2 0.30Example 3  71 27 8 0.08 0.6 4.0 0.3 5.0 0.25 Example 4  70 29 8 0.08 0.94.0 0.5 5.5 0.37 Example 5  66 30 6 0.08 0.6 4.0 0.3 5.0 0.25 Example 6 66 30 8 0.08 0.9 4.0 0.3 5.3 0.32 Example 7  66 30 8 0.08 0.7 3.6 0.34.7 0.30 Example 8  66 30 8 0.08 0.6 4.0 0.3 5.0 0.25 Example 9  66 30 80.08 0.6 4.0 0.3 5.0 0.25 Example 10 66 30 8 0.08 0.9 4.2 0.4 5.6 0.33Example 11 66 30 10 0.08 0.9 4.0 0.3 5.3 0.32 Example 12 66 30 6 0.080.9 4.0 0.3 5.3 0.32 Example 13 75 23 8 0.08 0.6 4.0 0.3 5.0 0.25Example 14 80 20 8 0.08 0.6 4.0 0.3 5.0 0.25 Example 15 66 30 11 0.080.6 4.0 0.3 5.0 0.25 Example 16 66 30 8 0.08 0.5 4.0 0.3 4.9 0.22Example 17 66 30 8 0.06 0.6 4.0 0.3 5.0 0.24 Example 18 66 30 8 0.04 0.64.0 0.3 4.9 0.24 Example 19 66 30 8 0.04 0.6 4.2 0.3 5.1 0.22 Example 2060 42 8 0.08 0.6 4.0 0.3 5.0 0.25 Example 21 65 35 8 0.10 0.8 4.0 0.35.2 0.30 Comparative 66 31 5 0.08 0.6 4.0 0.3 5.0 0.25 Example 1Comparative 66 31 10 0.08 1.0 4.0 0.3 5.4 0.35 Example 2 Comparative 6535 8 0.08 0.4 4.0 0.3 4.8 0.20 Example 3 Comparative 66 31 12 0.08 0.84.0 0.3 5.2 0.30 Example 4 Comparative 66 31 8 0.08 1.2 4.0 0.3 5.6 0.40Example 5 Comparative 66 31 8 0.08 0.9 4.1 0.6 5.7 0.39 Example 6Comparative 66 31 8 0.10 1.0 4.0 0.6 5.7 0.43 Example 7 FrictionMagnetic Magnetic powder Friction coefficient Amount Young's surfaceParticle coefficient ratio of width modulus roughness Aspect volumeratio (μ_(C(1000)))/ change [Gpa] R_(a) [nm] Type Shape ratio [nm³](μB/μA) μ_(C(5))) (μm) SNR Example 1  7.48 1.8 BaFe₁₂O₁₉ Plate shape 2.81950 1.2 1.2 4.3 0 Example 2  7.65 1.8 BaFe₁₂O₁₉ Plate shape 2.8 19501.2 1.2 4.6 0.1 Example 3  7.48 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.21.3 4.3 0.4 Example 4  7.89 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.25.0 0.3 Example 5  7.48 1.7 BaFe₁₂O₁₉ Plate shape 2.3 1300 1.5 1.6 4.30.1 Example 6  7.73 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.3 1.3 4.7 0.7Example 7  7.67 1.8 BaFe₁₂O₁₉ Plate shape 3.1 2000 1.2 1.2 4.2 0 Example8  7.48 1.8 ε iron oxide Spherical 1.1 2150 1.2 1.3 4.3 0.1 shapeExample 9  7.48 1.8 Co iron oxide Cubic shape 1.7 2200 1.2 1.2 4.3 0.2Example 10 7.76 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.1 5.0 0.1Example 11 7.73 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.6 1.8 4.7 0.1Example 12 7.73 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.2 4.7 0.6Example 13 7.48 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.4 1.5 4.3 0.5Example 14 7.48 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.6 1.6 4.3 0.7Example 15 7.48 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.8 1.8 4.3 0.1Example 16 7.39 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.6 1.6 4.2 0.0Example 17 7.46 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.2 4.3 0.4Example 18 7.45 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.2 4.3 0.6Example 19 6.43 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.2 4.7 0.6Example 20 7.48 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.3 4.3 −0.5Example 21 7.67 1.8 BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.3 4.6 −0.6Comparative 7.48 1.6 BaFe₁₂O₁₉ Plate shape 2.8 1950 2.2 2.3 4.3 0.1Example 1 Comparative 7.81 1.9 BaFe₁₂O₁₉ Plate shape 2.8 1950 2.3 1.84.9 0.7 Example 2 Comparative 7.30 1.7 BaFe₁₂O₁₉ Plate shape 2.8 19501.4 2.3 4.0 −0.5 Example 3 Comparative 7.65 2.0 BaFe₁₂O₁₉ Plate shape2.8 1950 2.1 2.0 4.6 0 Example 4 Comparative 7.96 1.9 BaFe₁₂O₁₉ Plateshape 2.8 1950 1.2 1.2 5.1 0 Example 5 Comparative 7.93 1.9 BaFe₁₂O₁₉Plate shape 2.8 1950 1.2 1.2 5.2 0 Example 6 Comparative 8.04 1.9BaFe₁₂O₁₉ Plate shape 2.8 1950 1.2 1.2 5.3 0 Example 7

The results illustrated in Table 1 indicate the following.

It is found that each of the magnetic tapes of Examples 1 to 21 hasfriction coefficient ratios (μ_(B)/μ_(A)) and (μ_(C(1000))/μ_(C(5))) of1.0 or more and 2.0 or less in spite of having a tape total thicknesst_(T) of 5.6 μm or less and an underlayer thickness of 0.5 m or more and0.9 μm or less, and has high traveling stability. Moreover, it is foundthat each of the magnetic tapes of Examples 1 to 20 has an amount ofwidth change of 4.0 μm or more and 5.0 μm or less and has good widthcontrollability. Therefore, it is found that the magnetic recordingmedium according to the present technology has excellent travelingstability and excellent width controllability in spite of having a thintotal thickness thereof and a thin underlayer.

Furthermore, comparison between the results of Examples 1 to 21 and theresults of Comparative Examples 5 to 7 indicates that widthcontrollability is improved by setting the Young's modulus of a magnetictape in the longitudinal direction to, for example, 7.90 Gpa or less.

Furthermore, by comparing the results of Examples 1 to 21 with theresult of Comparative Example 7, it is considered that the coating filmthickness/base thickness of, for example, 0.38 or less, contributes toimprovement in width controllability.

Furthermore, comparison between the results of Examples 1 to 21 and theresults of Comparative Examples 1 and 4 indicates that the frictioncoefficient ratios (μ_(B)/μ_(A)) and (μ_(C(1000))/μ_(C(5))) are wellcontrolled by setting the average diameter of the pores to 6 nm to 11nm, and traveling stability is improved.

Furthermore, comparison between the results of Examples 1 to 20 and theresults of Comparative Examples 2 and 3 indicates that the thickness ofthe underlayer of 0.5 am or more and 0.9 μm or less contributes toimprovement in traveling stability and SNR.

Furthermore, when Example 1 is compared with Example 20, in the former,the squareness ratio S2 was 65% and SNR was 0, whereas in the latter,the squareness ratio S2 was 60% and the SNR was −0.5. From this result,it is found that by setting the squareness ratio S2 to, for example, 65%or more, the SNR is further improved, that is, the recording/reproducingcharacteristics are improved.

Furthermore, comparison between Example 1 and Example 21 indicates thatthe SNR is further improved, that is, the recording/reproducingcharacteristics are improved by setting the thickness of the magneticlayer to, for example, 0.09 m or less, preferably 0.08 m or less.

The magnetic tapes of Examples 8 and 9 have about the same travelingstability and recording/reproducing characteristics as Example 1,although the type of magnetic powder is different from that ofExample 1. Therefore, it is found that the effect of the presenttechnology is exhibited even if the type of magnetic powder is changed.

Hereinabove, the embodiment and Examples of the present technology havebeen described specifically. However, the present technology is notlimited to the above-described embodiment and Examples, but variousmodifications based on the technical idea of the present technology canbe made.

For example, the configurations, the methods, the steps, the shapes, thematerials, the numerical values, and the like exemplified in theabove-described embodiment and Examples are only examples, and aconfiguration, a method, a step, a shape, a material, a numerical value,and the like different therefrom may be used as necessary. Furthermore,the chemical formulas of the compounds and the like are representativeand are not limited to the described valences and the like as long asthe compounds have common names of the same compound.

Furthermore, the configurations, the methods, the steps, the shapes, thematerials, the numerical values, and the like in the above-describedembodiment and Examples can be combined with one another as long as notdeparting from the gist of the present technology.

Furthermore, here, the numerical range indicated using “to” indicates arange including the numerical values described before and after “to” asthe minimum value and the maximum value, respectively. Within thenumerical range described step by step here, an upper limit value or alower limit value of a numerical range in one stage may be replaced withan upper limit value or a lower limit value of a numerical range inanother stage. The materials exemplified here can be used singly or incombination of two or more thereof unless otherwise specified.

Note that the present technology may have the following configurations.

[1] A tape-shaped magnetic recording medium including:

a magnetic layer; an underlayer; a base layer; and a back layer, inwhich

the underlayer has a thickness of 0.5 m or more and 0.9 μm or less,

the magnetic recording medium has an average thickness t_(T) of 5.6 μmor less,

the magnetic recording medium includes a lubricant,

the magnetic recording medium has pores, and the pores have an averagediameter of 6 nm or more and 11 nm or less when the diameters of thepores are measured in a state where the lubricant has been removed fromthe magnetic recording medium and the magnetic recording medium has beendried, and

the magnetic recording medium has Young's modulus of 7.90 GPa or less ina longitudinal direction thereof.

[2] The magnetic recording medium according to [1], having a squarenessratio of 65% or more in a perpendicular direction thereof.

[3] The magnetic recording medium according to [1] or [2], in which amagnetic layer side surface of the magnetic recording medium hasarithmetic average roughness R_(a) of 2.5 nm or less.

[4] The magnetic recording medium according to any one of [1] to [3], inwhich the magnetic layer has an average thickness t_(m) of 80 nm orless.

[5] The magnetic recording medium according to any one of [1] to [4], inwhich the base layer includes a polyester-based resin.

[6] The magnetic recording medium according to any one of [1] to [5], inwhich the ratio of the total thickness of the magnetic layer, theunderlayer, and the back layer to the thickness of the base layer is0.38 or less.

[7] The tape-shaped magnetic recording medium according to any one of[1] to [6], in which the amount of dimensional change of the magneticrecording medium in a width direction thereof between a state in which atension of 0.5 N is applied to the magnetic recording medium in alongitudinal direction thereof and a state in which a tension of 1.0 Nis applied to the magnetic recording medium in the longitudinaldirection is 4.0 μm or more and 5.0 μm or less.[8] The magnetic recording medium according to any one of [1] to [7], inwhich the magnetic layer includes magnetic powder, and the magneticpowder contains hexagonal ferrite, ε iron oxide, or Co iron oxide.[9] The magnetic recording medium according to [8], in which thehexagonal ferrite contains at least one of Ba or Sr, and the ε ironoxide contains at least one of Al or Ga.[10] The magnetic recording medium according to any one of [1] to [9],having a friction coefficient ratio (μ_(B)/μ_(A)) of 1.0 to 2.0, inwhich μ_(A) represents a coefficient of dynamic friction between amagnetic layer side surface of the magnetic recording medium and amagnetic head in a state where a tension of 0.4 N is applied to themagnetic recording medium in a longitudinal direction thereof, and μ_(B)represents a coefficient of dynamic friction between the magnetic layerside surface of the magnetic recording medium and the magnetic head in astate where a tension of 1.2 N is applied to the magnetic recordingmedium in the longitudinal direction.[11] The magnetic recording medium according to any one of [1] to [10],having a friction coefficient ratio (μ_(C(1000))/μ_(C(5))) of 1.0 to2.0, in which μ_(C(5)) represents a coefficient of dynamic friction atfifth reciprocation in a case where the magnetic recording medium in astate where a tension of 0.6 N is applied to the magnetic recordingmedium in a longitudinal direction thereof is reciprocatedly slid fivetimes on a magnetic head, and μ_(C(1000)) represents a coefficient ofdynamic friction at 1000th reciprocation in a case where the magneticrecording medium is reciprocated 1000 times on the magnetic head.[12] The magnetic recording medium according to any one of [1] to [11],in which the pores have an average diameter of 6 nm or more and 10 nm orless.[13] The magnetic recording medium according to any one of [1] to [12],in which the pores have an average diameter of 7 nm or more and 9 nm orless.[14] The magnetic recording medium according to any one of [1] to [13],in which the base layer has an average thickness of 4.2 μm or less.[15] The magnetic recording medium according to any one of [1] to [14],in which the back layer has an average thickness of 0.5 m or less.[16] The magnetic recording medium according to any one of [1] to [15],in which the magnetic layer includes magnetic powder, and the magneticpowder has an average aspect ratio of 1.0 or more and 3.5 or less.[17] A tape cartridge including:

the tape-shaped magnetic recording medium according to [1];

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in which

the information includes adjustment information for adjusting a tensionapplied to the magnetic recording medium in a longitudinal directionthereof.

[18] The tape cartridge according to [17], in which the adjustmentinformation includes dimensional information in a width direction at aplurality of positions in the longitudinal direction of the magneticrecording medium.

[19] A data processing method including:

a dimensional information acquiring step of acquiring dimensionalinformation in a width direction at a plurality of positions in alongitudinal direction of the tape-shaped magnetic recording mediumaccording to [1] while the magnetic recording medium is caused to travelwith a tension applied in the longitudinal direction; and

a data processing step of recording data on the magnetic recordingmedium and/or reproducing the data recorded on the magnetic recordingmedium while the magnetic recording medium is caused to travel with atension applied in the longitudinal direction, in which

in the data processing step, the tension applied to the magneticrecording medium in the longitudinal direction is adjusted on the basisof the dimensional information.

[20] The data processing method according to [19], in which in the dataprocessing step, the tension applied to the magnetic recording medium inthe longitudinal direction is adjusted on the basis of the dimensionalinformation and initial dimensional information acquired in advancebefore the dimensional information acquiring step is performed.[21] The data processing method according to [20], in which in the dataprocessing step, the tension applied to the magnetic recording medium inthe longitudinal direction is adjusted such that the dimensionalinformation corresponds to the initial dimensional information.[22] The data processing method according to any one of [19] to [21],further including

an information acquiring step of acquiring at least one of environmentalinformation around the magnetic recording medium or traveling conditioninformation, in which

in the data processing step, the tension applied to the magneticrecording medium in the longitudinal direction is adjusted on the basisof the dimensional information and at least one of the environmentalinformation or the traveling condition information.

[23] A tape-shaped magnetic recording medium including:

a magnetic layer; an underlayer; a base layer; and a back layer, inwhich

the underlayer has a thickness of 0.5 μm or more and 0.9 μm or less,

the magnetic recording medium has an average thickness t_(T) of 5.6 μmor less,

the magnetic recording medium includes a lubricant,

the magnetic recording medium has pores, and the pores have an averagediameter of 6 nm or more and 11 nm or less when the diameters of thepores are measured in a state where the lubricant has been removed fromthe magnetic recording medium and the magnetic recording medium has beendried, and

the ratio of the total thickness of the magnetic layer, the underlayer,and the back layer to the thickness of the base layer is 0.38 or less.

REFERENCE SIGNS LIST

-   10 Magnetic recording medium-   11 Base layer-   12 Underlayer-   13 Magnetic layer-   14 Back layer

The invention claimed is:
 1. A tape-shaped magnetic recording mediumcomprising: a magnetic layer; an underlayer; a base layer; and a backlayer, wherein the underlayer has a thickness of 0.5 μm or more and 0.9μm or less, the magnetic recording medium has an average thickness t_(T)of 5.6 μm or less, the magnetic recording medium includes a lubricant,the magnetic recording medium has pores, and the pores have an averagediameter of 6 nm or more and 11 nm or less when the diameters of thepores are measured in a state where the lubricant has been removed fromthe magnetic recording medium and the magnetic recording medium has beendried, and the magnetic recording medium has Young's modulus of 7.90 GPaor less in a longitudinal direction thereof; having a frictioncoefficient ratio (μ_(B)/μ_(A)) of 1.0 to 2.0, wherein μ_(A) representsa coefficient of dynamic friction between a magnetic layer side surfaceof the magnetic recording medium and a magnetic head in a state where atension of 0.4 N is applied to the magnetic recording medium in alongitudinal direction thereof, and μ_(B) represents a coefficient ofdynamic friction between the magnetic layer side surface of the magneticrecording medium and the magnetic head in a state where a tension of 1.2N is applied to the magnetic recording medium in the longitudinaldirection, wherein an amount of dimensional change of the magneticrecording medium in a width direction thereof between a state in which atension of 0.5 N is applied to the magnetic recording medium in alongitudinal direction thereof and a state in which a tension of 1.0 Nis applied to the magnetic recording medium in the longitudinaldirection is 4.0 μm or more and 5.0 μm or less.
 2. The magneticrecording medium according to claim 1, having a squareness ratio of 65%or more in a perpendicular direction thereof.
 3. The magnetic recordingmedium according to claim 1, wherein a magnetic layer side surface ofthe magnetic recording medium has arithmetic average roughness R_(a) of2.5 nm or less.
 4. The magnetic recording medium according to claim 1,wherein the magnetic layer has an average thickness t_(m) of 80 nm orless.
 5. The magnetic recording medium according to claim 1, wherein thebase layer includes a polyester as a main component.
 6. The magneticrecording medium according to claim 1, wherein a ratio of a totalthickness of the magnetic layer, the underlayer, and the back layer to athickness of the base layer is 0.38 or less.
 7. The magnetic recordingmedium according to claim 1, wherein the magnetic layer includesmagnetic powder, and the magnetic powder contains hexagonal ferrite,iron oxide, or Co iron oxide.
 8. The magnetic recording medium accordingto claim 7, wherein the hexagonal ferrite contains at least one of Ba orSr, and the ε iron oxide contains at least one of Al or Ga.
 9. Themagnetic recording medium according to claim 1, having a frictioncoefficient ratio (μ_(C(1000))/μ_(C(5))) of 1.0 to 2.0, wherein μ_(C(5))represents a coefficient of dynamic friction at fifth reciprocation in acase where the magnetic recording medium in a state where a tension of0.6 N is applied to the magnetic recording medium in a longitudinaldirection thereof is reciprocatedly slid five times on a magnetic head,and μ_(C(1000)) represents a coefficient of dynamic friction at 1000threciprocation in a case where the magnetic recording medium isreciprocated 1000 times on the magnetic head.
 10. The magnetic recordingmedium according to claim 1, wherein the pores have an average diameterof 6 nm or more and 10 nm or less.
 11. The magnetic recording mediumaccording to claim 1, wherein the pores have an average diameter of 7 nmor more and 9 nm or less.
 12. The magnetic recording medium according toclaim 1, wherein the base layer has an average thickness of 4.2 μm orless.
 13. The magnetic recording medium according to claim 1, whereinthe back layer has an average thickness of 0.5 μm or less.
 14. Themagnetic recording medium according to claim 1, wherein the magneticlayer includes magnetic powder, and the magnetic powder has an averageaspect ratio of 1.0 or more and 3.5 or less.